Zero vs Fastmail

Multi account

1. switcherConnect several accounts across providers — Gmail, Microsoft 365, IMAP — and work them from one place

   weight 3 · round to Fastmail
   Zero!disputedcontradicted4/10

   Zero's marketing repeatedly claims a 'Unified Inbox' connecting Gmail, Outlook, 'and more,' but the only hands-on/community description of the actual product (zero-comm-1) says it 'works on top of Gmail' and is in public beta, suggesting multi-provider (Microsoft 365, IMAP) support isn't yet realized in practice — no IMAP mention anywhere in the pack. Missing for 10: explicit IMAP support, confirmed working Microsoft 365/Outlook connection, and independent verification that multiple accounts can be worked from one place simultaneously.

   • [github] “Unified Inbox – Connect multiple email providers like Gmail, Outlook, and more.”
   • [github] “gives users the power to self-host their own email app while also integrating external services like Gmail and other email providers”
   • [community] “Zero founder describes it as an AI-powered email client that auto-categorizes, summarizes threads, drafts replies, and lets users chat with …”

   proof ↗⚑ flag

   Fastmail~partialcommunity6/10

   Fastmail explicitly documents importing mail from other providers and 'fetching mail from Gmail like a mail client' (IMAP-style pull), plus a 'Logging in to multiple accounts' feature and a dedicated Gmail-migration guide, and community reports confirm smooth Gmail-to-Fastmail migrations. However, evidence never mentions Microsoft 365/Exchange connectivity specifically, doesn't show a true unified single-inbox view merging external accounts (vs. separate logins), and one commenter notes migrating filters/rules doesn't come over cleanly. Missing for 10: explicit Microsoft 365/M365 account linking, detail on whether multiple accounts appear merged in one inbox view, and independent verification of multi-provider IMAP account aggregation beyond Gmail.

   • [community] “As an alternative to forwarding, you can also configure Fastmail to fetch mail from (and send via) Gmail like a mail client.”
   • [community] “Fastmail has an easy migration tool as well if you don't want to go the IMAP route. Now, migrating filters and rules over on the other hand.…”
   • [claimed-docs] “Import your mail”
   • [claimed-docs] “Logging in to multiple accounts”
   • [claimed-docs] “Move from Gmail”

   proof ↗⚑ flag

Portability

1. switcherMy mail stays reachable over open protocols and standard formats — IMAP/JMAP/SMTP access and standards-based export — so no client can lock me in

   weight 2 · round to Fastmail
   Zero—none0/10

   Evidence shows Zero connects to providers like Gmail/Outlook and offers self-hosting and an MCP server for AI actions, but nothing in the pack mentions IMAP/JMAP/SMTP protocol access or standards-based mail export for portability — the core of this switcher story is unaddressed.

   • [github] “Unified Inbox – Connect multiple email providers like Gmail, Outlook, and more.”
   • [github] “gives users the power to self-host their own email app while also integrating external services like Gmail and other email providers”
   • [github] “Self-Hosting Freedom – Run your own email app with ease.”
   • [claimed-docs] “Self-hosting capabilities”

   proof ↗⚑ flag

   Fastmail✓fullcommunity8/10

   Fastmail documents JMAP (open standard) and IMAP/SMTP access via API tokens/app passwords, plus import/export tooling for migration, and community reports confirm SMTP/IMAP interoperability with other providers (e.g., fetching Gmail via IMAP, app passwords for SMTP). This directly supports open-protocol reachability and avoiding lock-in. Missing for 10: explicit documentation of full mail export/backup format standards (e.g., mbox/EML export) and independent verification of IMAP feature parity beyond anecdotal mentions.

   • [claimed-docs] “Fetch `/.well-known/jmap` for the session object - capabilities, accounts, and all API URLs.”
   • [claimed-docs] “JMAP is an open standard any organisation can implement, not more proprietary lock-in from big tech companies.”
   • [claimed-docs] “Open source and standards | Fastmail”
   • [claimed-docs] “API tokens”
   • [claimed-docs] “Import your mail”
   • [community] “As an alternative to forwarding, you can also configure Fastmail to fetch mail from (and send via) Gmail like a mail client.”
   • [community] “I just use SMTP for this (with FastMail). FastMail is not really intended for [transactional emails at scale] as the limits and the like don…”
   • [community] “Fastmail has an easy migration tool as well if you don't want to go the IMAP route. Now, migrating filters and rules over on the other hand.…”

   proof ↗⚑ flag

2. switcherSelf-host the email app and keep the mail pipeline under my own control

   weight 1 · round to Zero
   Zero✓fullprobed7/10

   Zero is explicitly open-source and self-hostable, with GitHub docs stating 'Self-Hosting Freedom – Run your own email app with ease' and a probe confirming a real, keyless-cloneable source tree with docker-compose files for self-hosting the full mail pipeline (DB, prod services). This gives a switcher genuine control over their own instance rather than relying on a hosted SaaS. Missing for 10: detailed self-hosting setup/migration docs (e.g. IMAP/SMTP backend specifics), independent hands-on reports of a completed self-hosted deployment, and confirmation of full mailbox portability beyond Gmail/Outlook OAuth integration.

   • [github] “Self-Hosting Freedom – Run your own email app with ease.”
   • [github] “⚙️ Self-Hosting Freedom – Run your own email app with ease.”
   • [github] “gives users the power to **self-host** their own email app”
   • [github] “gives users the power to self-host their own email app while also integrating external services like Gmail and other email providers”
   • [probe] “PROBE runtime (recorded 2026-09-06): a keyless shallow git clone of Mail-0/Zero landed a REAL self-hostable source tree — repo-root MCP.md (…”
   • [claimed-docs] “Self-hosting capabilities”

   proof ↗⚑ flag

   Fastmail—none0/10

   The axis applies to this product kind (peer products hold positive or none verdicts on this story), so lack of evidence for an applicable capability is "none", never "na". (na/none harmonized at arena bring-up — see pipeline/scripts/na-harmonize.ts.)

   ⚑ flag

Agent access

1. ai-native userPoint an agent at llms.txt or agent-oriented docs

   weight 2 · round to Zero
   Zero~partialprobed6/10

   The repo ships an AGENT.md (agent-configuration doc) and a detailed MCP.md describing the MCP server's tool surface, both of which are exactly the kind of machine/agent-oriented documentation an AI agent could be pointed at; this was confirmed by a hands-on probe of the actual repo tree. However there is no evidence of a dedicated llms.txt file or any explicit guidance framing these docs as an 'agent-readable spec' in the llms.txt convention. Missing for 10: an actual llms.txt file, first-party statement that docs are structured for LLM consumption, and independent confirmation an agent successfully parsed these docs.

   • [probe] “PROBE runtime (recorded 2026-09-06): a keyless shallow git clone of Mail-0/Zero landed a REAL self-hostable source tree — repo-root MCP.md (…”
   • [probe] “official MCP server documented at https://github.com/Mail-0/Zero/blob/staging/MCP.md”
   • [claimed-docs] “You can connecto ZeroMCP using two methods: 1. Better Auth session token 2. OAuth (Coming soon)”
   • [claimed-docs] “Compose emails with AI assistance - Ask questions about mailbox content - Ask questions about specific email threads - Web search using Perp…”

   proof ↗⚑ flag

   Fastmail—none0/10

   A direct probe confirms no llms.txt exists (404) and no openapi/agent-oriented discovery docs were found either; while JMAP API docs exist, there is no evidence of an llms.txt or agent-oriented documentation entry point.

   • [probe] “PROBE llms.txt: HTTP 404 at https://www.fastmail.help/llms.txt”
   • [probe] “PROBE openapi: all candidate paths 404 (https://www.fastmail.help/openapi.json, https://www.fastmail.help/swagger.json, https://www.fastmail…”

   proof ↗⚑ flag

2. ai-native userRun the product headlessly / in CI for automation

   weight 2 · round to Fastmail
   Zero—none0/10

   The axis applies to this product kind (peer products hold positive or none verdicts on this story), so lack of evidence for an applicable capability is "none", never "na". (na/none harmonized at arena bring-up — see pipeline/scripts/na-harmonize.ts.)

   ⚑ flag

   Fastmail~partialcommunity5/10

   Fastmail exposes a documented JMAP API and API tokens/OAuth for programmatic access (fastmail-docs-1,2,5,22,40), and community evidence confirms it can be driven via SMTP/app passwords for scripted/automated sending (fastmail-comm-11), which supports headless use in scripts or CI. However, there is no explicit CI/headless-mode documentation, no official CLI, and community feedback notes it isn't built for large-scale automated/transactional use. Missing for 10: dedicated CI/automation documentation or examples, an official CLI, and confirmation of headless reliability at scale.

   • [claimed-docs] “Fetch `/.well-known/jmap` for the session object - capabilities, accounts, and all API URLs.”
   • [claimed-docs] “Standard OAuth 2.0 or Bearer tokens. No custom auth protocol to implement. Works with what you already have.”
   • [claimed-docs] “API tokens”
   • [claimed-docs] “API Documentation”
   • [community] “I just use SMTP for this (with FastMail). FastMail is not really intended for [transactional emails at scale] as the limits and the like don…”

   proof ↗⚑ flag

3. ai-native userPlug MCP servers into this product so it can use their tools

   weight 3 · round drawn
   Zero—none0/10

   All evidence describes Zero exposing its own email/label/compose tools via an official 'ZeroMCP' server for other AI agents to consume — i.e., Zero acting as an MCP server/provider, not as a client that plugs in external MCP servers to use their tools. There is no documentation of Zero itself connecting to third-party MCP servers to extend its own toolset.

   • [claimed-docs] “You can connecto ZeroMCP using two methods: 1. Better Auth session token 2. OAuth (Coming soon)”
   • [probe] “official MCP server documented at https://github.com/Mail-0/Zero/blob/staging/MCP.md”
   • [probe] “PROBE runtime (recorded 2026-09-06): a keyless shallow git clone of Mail-0/Zero landed a REAL self-hostable source tree — repo-root MCP.md (…”
   • [claimed-docs] “Compose emails with AI assistance - Ask questions about mailbox content - Ask questions about specific email threads - Web search using Perp…”

   proof ↗⚑ flag

   Fastmail—none0/10

   The axis applies to this product kind (peer products hold positive or none verdicts on this story), so lack of evidence for an applicable capability is "none", never "na". (na/none harmonized at arena bring-up — see pipeline/scripts/na-harmonize.ts.)

   ⚑ flag

4. ai-native userConnect an agent via an official MCP server

   weight 3 · round to Zero
   Zero✓fullprobed8/10

   Zero ships a documented, named 'Zero MCP' server (MCP.md) exposing concrete tools (email CRUD, labels, AI compose, mailbox Q&A, web search) with an authentication method (Better Auth session token, OAuth coming soon), confirmed by an independent runtime probe finding the file in the actual repo. Missing for 10: independent hands-on verification that a third-party agent successfully connects and uses the server end-to-end, and OAuth is still unimplemented.

   • [claimed-docs] “You can connecto ZeroMCP using two methods: 1. Better Auth session token 2. OAuth (Coming soon)”
   • [claimed-docs] “Get email threads by ID - List emails in specific folders - Create and send new emails - Create email drafts - Send existing drafts - Delete…”
   • [claimed-docs] “Compose emails with AI assistance - Ask questions about mailbox content - Ask questions about specific email threads - Web search using Perp…”
   • [probe] “official MCP server documented at https://github.com/Mail-0/Zero/blob/staging/MCP.md”
   • [probe] “PROBE runtime (recorded 2026-09-06): a keyless shallow git clone of Mail-0/Zero landed a REAL self-hostable source tree — repo-root MCP.md (…”

   proof ↗⚑ flag

   Fastmail—none0/10

   Fastmail exposes JMAP and API tokens for developers, but there is no evidence of an official MCP server or endpoint that lets AI agents connect natively; probes for machine-readable spec files (llms.txt, openapi) both return 404.

   • [claimed-docs] “Fetch `/.well-known/jmap` for the session object - capabilities, accounts, and all API URLs.”
   • [claimed-docs] “API tokens”
   • [probe] “PROBE llms.txt: HTTP 404 at https://www.fastmail.help/llms.txt”
   • [probe] “PROBE openapi: all candidate paths 404 (https://www.fastmail.help/openapi.json, https://www.fastmail.help/swagger.json, https://www.fastmail…”

   proof ↗⚑ flag

5. ai-native userUse an official CLI

   weight 2 · round drawn
   Zero—none0/10

   Zero's evidence shows an MCP server (ZeroMCP) and self-hosting via docker-compose, plus a pnpm-based dev script for Drizzle Studio, but no official CLI tool for AI-native interaction with the product itself is documented anywhere in the pack.

   • [claimed-docs] “You can connecto ZeroMCP using two methods: 1. Better Auth session token 2. OAuth (Coming soon)”
   • [claimed-docs] “View and edit data with Drizzle Studio pnpm db:studio”
   • [probe] “official MCP server documented at https://github.com/Mail-0/Zero/blob/staging/MCP.md”

   proof ↗⚑ flag

   Fastmail—none0/10

   Evidence shows JMAP API, tokens, and OAuth support, but there is no mention of an official CLI tool for Fastmail; probes for llms.txt/openapi also returned 404s, and no CLI is referenced anywhere in docs or community posts.

   ⚑ flag

6. ai-native userDrive the product through a documented public API

   weight 3 · round drawn
   Zero✓fullprobed8/10

   Zero ships a documented MCP server (ZeroMCP) exposing a public, structured API for emails, labels, AI compose, mailbox Q&A, and web search, with authentication documented via Better Auth session tokens (OAuth coming soon), corroborated by a runtime probe confirming the real MCP.md and AGENT.md files in the repo. missing for 10: independent third-party usage/testing of the MCP API beyond first-party docs and a single runtime probe, and full OAuth support (currently listed as coming soon).

   • [claimed-docs] “You can connecto ZeroMCP using two methods: 1. Better Auth session token 2. OAuth (Coming soon)”
   • [claimed-docs] “Get email threads by ID - List emails in specific folders - Create and send new emails - Create email drafts - Send existing drafts - Delete…”
   • [claimed-docs] “Compose emails with AI assistance - Ask questions about mailbox content - Ask questions about specific email threads - Web search using Perp…”
   • [probe] “official MCP server documented at https://github.com/Mail-0/Zero/blob/staging/MCP.md”
   • [probe] “PROBE runtime (recorded 2026-09-06): a keyless shallow git clone of Mail-0/Zero landed a REAL self-hostable source tree — repo-root MCP.md (…”

   proof ↗⚑ flag

   Fastmail✓fullclaimed8/10

   Fastmail publishes JMAP, an open, documented API protocol with a discoverable session endpoint, standard OAuth2/Bearer auth, API tokens, push via EventSource/WebPush, and a dedicated dev docs page (fastmail.com/dev), giving AI-native users a clear, standards-based way to programmatically drive the product. Missing for 10: no evidence of an OpenAPI/Swagger spec or llms.txt (probes returned 404s) and no independent third-party corroboration of API robustness beyond vendor docs.

   • [claimed-docs] “Fetch `/.well-known/jmap` for the session object - capabilities, accounts, and all API URLs.”
   • [claimed-docs] “Standard OAuth 2.0 or Bearer tokens. No custom auth protocol to implement. Works with what you already have.”
   • [claimed-docs] “Get instant push via EventSource — one connection, all mailboxes. Or use WebPush for mobile-compatible push, no permanent connection require…”
   • [claimed-docs] “Sync changes more easily, more efficiently, and much, much faster. A single HTTP roundtrip is often all that's required.”
   • [claimed-docs] “API tokens”
   • [claimed-docs] “POST a `methodCalls` array. Query, fetch, and send, all in one HTTP request.”
   • [claimed-docs] “API Documentation”
   • [claimed-docs] “Standard OAuth 2.0 or Bearer tokens. No custom auth protocol to implement.”

   proof ↗⚑ flag

7. ai-native userIssue scoped/least-privilege API credentials for an agent

   weight 2 · round to Fastmail
   Zero—none0/10

   Zero's MCP server documents authentication via a Better Auth session token (or future OAuth), but there is no evidence of scoped or least-privilege credential issuance, permission granularity, or agent-specific token scoping — auth appears to be a single session-level token granting full account access. Missing for 10: any documentation of scopes/permissions models, per-agent credential minting, or restricted-access tokens for agents.

   • [claimed-docs] “You can connecto ZeroMCP using two methods: 1. Better Auth session token 2. OAuth (Coming soon)”
   • [probe] “PROBE runtime (recorded 2026-09-06): a keyless shallow git clone of Mail-0/Zero landed a REAL self-hostable source tree — repo-root MCP.md (…”

   proof ↗⚑ flag

   Fastmail~partialcommunity6/10

   Fastmail provides API tokens (fastmail-docs-5/22) and OAuth2/Bearer token support (fastmail-docs-2/41) for JMAP access, and community evidence confirms real-world scoped 'app passwords' limited to a single protocol like SMTP (fastmail-comm-11), showing least-privilege credential issuance works in practice. However, the docs are only titles with no detail on fine-grained scope configuration for agent-specific use cases, and there's no explicit agent/AI-oriented credential guidance. Missing for 10: detailed scope/permission granularity documentation, explicit agent-use-case guidance, and independent hands-on verification of scoping API tokens (not just app passwords) for AI agents.

   • [claimed-docs] “API tokens”
   • [claimed-docs] “API tokens – Fastmail”
   • [claimed-docs] “Standard OAuth 2.0 or Bearer tokens. No custom auth protocol to implement. Works with what you already have.”
   • [claimed-docs] “Standard OAuth 2.0 or Bearer tokens. No custom auth protocol to implement.”
   • [community] “I just use SMTP for this (with FastMail). FastMail is not really intended for [transactional emails at scale] as the limits and the like don…”

   proof ↗⚑ flag

8. ai-native userBuild against official SDKs

   weight 2 · round to Zero
   Zero~partialprobed5/10

   Zero doesn't publish a traditional language SDK, but it does document an official 'ZeroMCP' server (MCP.md) with concrete tool endpoints (email CRUD, labels, AI compose, mailbox Q&A) plus AGENT.md agent-configuration docs, giving AI-native developers a documented, official programmatic interface to build against, corroborated by a runtime probe confirming these files exist in the live repo. Missing for 10: an actual client SDK/library (Python/JS package), auth beyond a session token (OAuth marked 'coming soon'), and independent third-party developer usage reports.

   • [claimed-docs] “Modify email labels”
   • [claimed-docs] “You can connecto ZeroMCP using two methods: 1. Better Auth session token 2. OAuth (Coming soon)”
   • [claimed-docs] “Get email threads by ID - List emails in specific folders - Create and send new emails - Create email drafts - Send existing drafts - Delete…”
   • [probe] “official MCP server documented at https://github.com/Mail-0/Zero/blob/staging/MCP.md”
   • [probe] “PROBE runtime (recorded 2026-09-06): a keyless shallow git clone of Mail-0/Zero landed a REAL self-hostable source tree — repo-root MCP.md (…”
   • [github] “🚀 Developer-Friendly – Built with extensibility and integrations in mind.”

   proof ↗⚑ flag

   Fastmail—none0/10

   Fastmail documents the JMAP protocol and a developer API page, but the evidence never mentions any official SDKs (client libraries) for languages/frameworks — only raw protocol specs, API tokens, and a dev docs page. Probes for machine-readable API discovery (llms.txt, openapi) also 404, reinforcing the absence of packaged SDK tooling.

   • [claimed-docs] “API Documentation”
   • [claimed-docs] “API tokens”
   • [probe] “PROBE llms.txt: HTTP 404 at https://www.fastmail.help/llms.txt”
   • [probe] “PROBE openapi: all candidate paths 404 (https://www.fastmail.help/openapi.json, https://www.fastmail.help/swagger.json, https://www.fastmail…”

   proof ↗⚑ flag

9. ai-native userSubscribe to events via webhooks

   weight 2 · round to Fastmail
   Zero—none0/10

   Evidence covers Zero's MCP server (tool-calling actions like search, compose, label management) but nowhere mentions webhooks, event subscriptions, or push notifications for external systems to react to inbox events.

   ⚑ flag

   Fastmail~partialclaimed5/10

   Fastmail's JMAP API supports push/event notification via EventSource (SSE) and WebPush, which lets clients subscribe to mailbox changes without polling — a webhook-adjacent mechanism (docs-3, docs-19). However, there's no explicit documentation of a classic webhook (HTTP callback URL registration) API, and no independent/hands-on confirmation of setting up such subscriptions. Missing for 10: explicit webhook callback-URL registration docs, third-party confirmation of push reliability, and any mention of 'webhook' terminology in official docs.

   • [claimed-docs] “Get instant push via EventSource — one connection, all mailboxes. Or use WebPush for mobile-compatible push, no permanent connection require…”
   • [claimed-docs] “Get instant push via EventSource — one connection, all mailboxes.”
   • [claimed-docs] “POST a `methodCalls` array. Query, fetch, and send, all in one HTTP request.”
   • [claimed-docs] “API Documentation”

   proof ↗⚑ flag

Agentic features

1. ai-native userGet AI-generated insights and suggestions from my data inside the product

   weight 2 · round to Zero
   Zero✓fullprobed7/10

   Zero documents AI features that generate insights from mailbox data: composing emails with AI assistance, answering questions about mailbox content and specific threads, and summarizing/chatting with inbox content, corroborated by founder description of AI-powered summarization and chat-with-inbox in community coverage. missing for 10: independent hands-on verification of insight quality/accuracy and no broader third-party review confirming these AI features work reliably in practice.

   • [claimed-docs] “Ask questions about specific email threads”
   • [claimed-docs] “Ask questions about mailbox content - Ask questions about specific email threads”
   • [claimed-docs] “Compose emails with AI assistance - Ask questions about mailbox content - Ask questions about specific email threads - Web search using Perp…”
   • [community] “Zero founder describes it as an AI-powered email client that auto-categorizes, summarizes threads, drafts replies, and lets users chat with …”
   • [probe] “PROBE runtime (recorded 2026-09-06): a keyless shallow git clone of Mail-0/Zero landed a REAL self-hostable source tree — repo-root MCP.md (…”

   proof ↗⚑ flag

   Fastmail—none0/10

   No evidence of any AI-generated insights, summaries, or suggestions within Fastmail's product; the evidence pack covers JMAP protocol, filters, search, aliases, masked email, and other traditional email features but nothing about AI-driven analysis of user data.

   ⚑ flag

2. ai-native userSet up automations that run autonomously in the background

   weight 2 · round to Fastmail
   Zero—none0/10

   Evidence shows an MCP server exposing on-demand email tools (search, compose, label, delete) that an AI client can call interactively, but nothing shows Zero itself scheduling or running autonomous background automations/triggers/workflows without a user or agent actively invoking them.

   ⚑ flag

   Fastmail~partialclaimed5/10

   Fastmail's Filters & Rules feature provides server-side automation that runs autonomously in the background without user intervention, and JMAP API tokens plus EventSource/WebPush push notifications allow building custom automated workflows (e.g., an agent reacting to new mail events). However, there is no evidence of purpose-built AI-agent automation tooling, scheduled/triggered agent workflows, or third-party AI automation integrations. Missing for 10: dedicated AI/agent automation framework or examples, evidence of autonomous multi-step workflows beyond simple filters, independent confirmation of using JMAP for agentic background tasks.

   • [claimed-docs] “Filters & Rules”
   • [claimed-docs] “Filters & Rules – Fastmail”
   • [claimed-docs] “Get instant push via EventSource — one connection, all mailboxes. Or use WebPush for mobile-compatible push, no permanent connection require…”
   • [claimed-docs] “Get instant push via EventSource — one connection, all mailboxes.”
   • [claimed-docs] “API tokens”
   • [claimed-docs] “API tokens – Fastmail”
   • [claimed-docs] “POST a `methodCalls` array. Query, fetch, and send, all in one HTTP request.”

   proof ↗⚑ flag

3. ai-native userDelegate tasks to a built-in AI assistant inside the product

   weight 3 · round to Zero
   Zero✓fullprobed8/10

   Zero ships a built-in AI assistant that can compose emails, answer questions about threads/mailbox, and perform web search (Perplexity), confirmed both in docs (MCP.md) and independent community description of it as an 'AI-powered email client' that summarizes, drafts, and lets users chat with their inbox. Missing for 10: broader independent hands-on verification beyond a single HN comment, and clearer distinction between MCP-exposed tools vs. in-app assistant UX.

   • [claimed-docs] “Compose emails with AI assistance”
   • [claimed-docs] “Ask questions about specific email threads”
   • [claimed-docs] “Ask questions about mailbox content - Ask questions about specific email threads”
   • [claimed-docs] “Compose emails with AI assistance - Ask questions about mailbox content - Ask questions about specific email threads - Web search using Perp…”
   • [community] “Zero founder describes it as an AI-powered email client that auto-categorizes, summarizes threads, drafts replies, and lets users chat with …”
   • [probe] “PROBE runtime (recorded 2026-09-06): a keyless shallow git clone of Mail-0/Zero landed a REAL self-hostable source tree — repo-root MCP.md (…”

   proof ↗⚑ flag

   Fastmail—none0/10

   The axis applies to this product kind (peer products hold positive or none verdicts on this story), so lack of evidence for an applicable capability is "none", never "na". (na/none harmonized at arena bring-up — see pipeline/scripts/na-harmonize.ts.)

   ⚑ flag

4. ai-native userOperate the product with natural-language commands

   weight 2 · round to Zero
   Zero✓fullcommunity7/10

   Zero's founder describes it as an AI-powered email client where users can chat with their inbox, ask questions about threads, and have AI draft replies, and the MCP docs confirm natural-language driven actions (compose, search, ask questions, web search) — this directly matches AI-native NL command operation. Missing for 10: independent hands-on verification of the actual chat UI/NL command interface beyond founder claims and MCP protocol docs.

   • [community] “Zero founder describes it as an AI-powered email client that auto-categorizes, summarizes threads, drafts replies, and lets users chat with …”
   • [claimed-docs] “Ask questions about specific email threads”
   • [claimed-docs] “Ask questions about mailbox content - Ask questions about specific email threads”
   • [claimed-docs] “Compose emails with AI assistance - Ask questions about mailbox content - Ask questions about specific email threads - Web search using Perp…”
   • [claimed-docs] “Compose emails with AI assistance”

   proof ↗⚑ flag

   Fastmail—none0/10

   No evidence of any natural-language command interface, chat assistant, or NL-to-action layer in Fastmail; the product exposes a structured JMAP API and traditional GUI/keyboard shortcuts, not NL commands. Probes for llms.txt and OpenAPI (which could hint at AI-native tooling) returned 404s, further indicating absence.

   • [probe] “PROBE llms.txt: HTTP 404 at https://www.fastmail.help/llms.txt”
   • [probe] “PROBE openapi: all candidate paths 404 (https://www.fastmail.help/openapi.json, https://www.fastmail.help/swagger.json, https://www.fastmail…”
   • [claimed-docs] “Keyboard shortcuts”

   proof ↗⚑ flag

Api quality

1. ai-native userExplore an interactive API reference with runnable examples

   weight 2 · round drawn
   Zero—none0/10

   Zero is an email client with an MCP server and docs (MCP.md, ROADMAP.md), but there is no evidence of an interactive API reference (e.g., Swagger/OpenAPI explorer, Postman collection, or runnable code sandbox) for AI-native users to explore and execute example calls.

   ⚑ flag

   Fastmail—none0/10

   Fastmail provides JMAP protocol documentation and a developer docs page (fastmail-docs-40), but there is no evidence of an interactive API reference with runnable/try-it-now examples; probes for OpenAPI/Swagger specs and llms.txt both returned 404s (fastmail-probe-1, fastmail-probe-2), indicating no such interactive tooling exists.

   • [claimed-docs] “API Documentation”
   • [probe] “PROBE llms.txt: HTTP 404 at https://www.fastmail.help/llms.txt”
   • [probe] “PROBE openapi: all candidate paths 404 (https://www.fastmail.help/openapi.json, https://www.fastmail.help/swagger.json, https://www.fastmail…”

   proof ↗⚑ flag

2. ai-native userDownload a machine-readable API spec (OpenAPI or equivalent)

   weight 2 · round to Fastmail
   Zero—none0/10

   The axis applies to this product kind (peer products hold positive or none verdicts on this story), so lack of evidence for an applicable capability is "none", never "na". (na/none harmonized at arena bring-up — see pipeline/scripts/na-harmonize.ts.)

   ⚑ flag

   Fastmail~partialprobed4/10

   Fastmail's JMAP protocol provides a machine-readable session/capabilities discovery endpoint (/.well-known/jmap) and points to formal JMAP specs, plus a general 'API Documentation' page, which partially satisfies the spirit of a machine-readable API description even though it isn't an OpenAPI document. However, direct probes for openapi.json/swagger.json/llms.txt all return 404, showing no actual downloadable OpenAPI-equivalent artifact is published. Missing for 10: an actual downloadable OpenAPI/Swagger/JSON-Schema file, confirmation that fastmail.com/dev/ hosts a structured machine-readable spec rather than prose docs, and independent verification of spec completeness.

   • [claimed-docs] “Fetch `/.well-known/jmap` for the session object - capabilities, accounts, and all API URLs.”
   • [claimed-docs] “API Documentation”
   • [probe] “PROBE llms.txt: HTTP 404 at https://www.fastmail.help/llms.txt”
   • [probe] “PROBE openapi: all candidate paths 404 (https://www.fastmail.help/openapi.json, https://www.fastmail.help/swagger.json, https://www.fastmail…”

   proof ↗⚑ flag

3. ai-native userTest against a sandbox environment without touching production data

   weight 1 · round drawn
   Zero—none0/10

   Zero is an AI email client whose evidence covers MCP tools for real mailbox operations (send/delete/label emails) and self-hosting, but nothing describes a sandbox, test/staging mode, or mock data environment isolated from production email accounts.

   ⚑ flag

   Fastmail—none0/10

   No evidence of a sandbox, staging, or test environment for developers to use with the JMAP API separate from production data; docs only describe production API access via OAuth/Bearer tokens.

   ⚑ flag

4. ai-native userRely on versioned APIs with a documented deprecation policy

   weight 2 · round drawn
   Zero—none0/10

   Evidence describes Zero's MCP server capabilities and self-hosting, but no documentation anywhere mentions API versioning, version numbers, or a deprecation policy for its MCP/API surface. missing for 10: any mention of API versioning scheme, changelog/deprecation policy, or backward-compatibility guarantees.

   ⚑ flag

   Fastmail—none0/10

   Evidence shows Fastmail's JMAP API and documentation (session discovery, OAuth, API tokens, dev docs) but no mention of API versioning scheme or a documented deprecation policy; probes for openapi/llms.txt also 404, suggesting no machine-readable spec exists either.

   • [claimed-docs] “Fetch `/.well-known/jmap` for the session object - capabilities, accounts, and all API URLs.”
   • [claimed-docs] “API Documentation”
   • [probe] “PROBE llms.txt: HTTP 404 at https://www.fastmail.help/llms.txt”
   • [probe] “PROBE openapi: all candidate paths 404 (https://www.fastmail.help/openapi.json, https://www.fastmail.help/swagger.json, https://www.fastmail…”

   proof ↗⚑ flag

Agent workflows

1. ai-native userAn external agent — Claude, ChatGPT, or my own — can read, triage, draft, and send my email end to end through a documented connection

   weight 2 · round to Zero
   Zero✓fullprobed8/10

   Zero documents an official MCP server (MCP.md, verified by probe) enabling agents like Claude to read threads, ask questions about mailbox content, compose with AI assistance, and create/send drafts and new emails, plus manage labels — covering triage, drafting, and sending end to end via Better Auth session token auth. missing for 10: no hands-on third-party report of an external agent (Claude/ChatGPT) actually completing a full read-triage-send workflow, and OAuth support is still 'coming soon' rather than shipped.

   • [claimed-docs] “Compose emails with AI assistance”
   • [claimed-docs] “Ask questions about specific email threads”
   • [claimed-docs] “Ask questions about mailbox content - Ask questions about specific email threads”
   • [claimed-docs] “Get email threads by ID - List emails in specific folders - Create and send new emails - Create email drafts - Send existing drafts - Delete…”
   • [claimed-docs] “Compose emails with AI assistance - Ask questions about mailbox content - Ask questions about specific email threads - Web search using Perp…”
   • [claimed-docs] “You can connecto ZeroMCP using two methods: 1. Better Auth session token 2. OAuth (Coming soon)”
   • [probe] “official MCP server documented at https://github.com/Mail-0/Zero/blob/staging/MCP.md”
   • [probe] “PROBE runtime (recorded 2026-09-06): a keyless shallow git clone of Mail-0/Zero landed a REAL self-hostable source tree — repo-root MCP.md (…”

   proof ↗⚑ flag

   Fastmail~partialprobed5/10

   Fastmail exposes a fully documented JMAP API with OAuth2/Bearer token auth and API tokens (fastmail-docs-1,2,5,38,41) that could let a custom-built agent read, query, and send mail via standard HTTP, satisfying the 'my own agent' case. But there is no evidence of an official MCP server, ChatGPT/Claude connector, or any first-party documented integration enabling Claude or ChatGPT specifically to triage/draft/send end-to-end — probes for llms.txt and OpenAPI discovery both returned 404 (fastmail-probe-1, fastmail-probe-2). Missing for 10: official MCP server or Claude/ChatGPT plugin, documented end-to-end agent workflow (triage+draft+send), and independent evidence of an AI agent actually operating through this API.

   • [claimed-docs] “Fetch `/.well-known/jmap` for the session object - capabilities, accounts, and all API URLs.”
   • [claimed-docs] “Standard OAuth 2.0 or Bearer tokens. No custom auth protocol to implement. Works with what you already have.”
   • [claimed-docs] “API tokens”
   • [claimed-docs] “POST a `methodCalls` array. Query, fetch, and send, all in one HTTP request.”
   • [claimed-docs] “Standard OAuth 2.0 or Bearer tokens. No custom auth protocol to implement.”
   • [probe] “PROBE llms.txt: HTTP 404 at https://www.fastmail.help/llms.txt”
   • [probe] “PROBE openapi: all candidate paths 404 (https://www.fastmail.help/openapi.json, https://www.fastmail.help/swagger.json, https://www.fastmail…”

   proof ↗⚑ flag

Ai assistant

1. ai-native userAsk an assistant questions across my whole inbox and calendar — who said what, what's outstanding — and get grounded answers

   weight 2 · round to Zero
   Zero~partialprobed6/10

   Zero's MCP server explicitly supports asking questions about mailbox content and specific email threads, plus AI compose, search, and labels, and community commentary confirms an AI-powered 'chat with your inbox' experience. However, evidence doesn't show cross-inbox/whole-calendar synthesis, calendar integration, or 'who said what / what's outstanding' style grounded multi-thread reasoning — the documented Q&A appears scoped to mailbox/thread level rather than full inbox+calendar grounding. missing for 10: calendar integration/awareness, evidence of synthesizing across the entire inbox (not just single threads), independent hands-on verification of grounded multi-source answers.

   • [claimed-docs] “Ask questions about specific email threads”
   • [claimed-docs] “Ask questions about mailbox content - Ask questions about specific email threads”
   • [claimed-docs] “Compose emails with AI assistance - Ask questions about mailbox content - Ask questions about specific email threads - Web search using Perp…”
   • [community] “Zero founder describes it as an AI-powered email client that auto-categorizes, summarizes threads, drafts replies, and lets users chat with …”
   • [probe] “PROBE runtime (recorded 2026-09-06): a keyless shallow git clone of Mail-0/Zero landed a REAL self-hostable source tree — repo-root MCP.md (…”

   proof ↗⚑ flag

   Fastmail—none0/10

   There is no evidence of any Fastmail-native AI assistant, chat interface, or grounded Q&A feature over inbox/calendar content; evidence only covers JMAP API access, standard mail features, and general product satisfaction. A third party could build such an assistant using JMAP/API tokens, but no evidence shows Fastmail itself offers this capability.

   • [claimed-docs] “Fetch `/.well-known/jmap` for the session object - capabilities, accounts, and all API URLs.”
   • [claimed-docs] “API tokens”
   • [claimed-docs] “API Documentation”

   proof ↗⚑ flag

Ai drafting

1. ai-native userAI drafts replies in my own voice and tone — ready to review and send, not generic boilerplate

   weight 3 · round to Zero
   Zero~partialcommunity5/10

   Zero's MCP docs and founder description confirm AI drafts replies ('Compose emails with AI assistance', 'drafts replies') as a core feature, but no evidence describes voice/tone personalization or learning the user's writing style. Missing for 10: documentation of voice/tone matching or personalization mechanism, and independent hands-on verification that drafts read as the user's own voice rather than generic AI text.

   • [claimed-docs] “Compose emails with AI assistance”
   • [claimed-docs] “Compose emails with AI assistance - Ask questions about mailbox content - Ask questions about specific email threads - Web search using Perp…”
   • [community] “Zero founder describes it as an AI-powered email client that auto-categorizes, summarizes threads, drafts replies, and lets users chat with …”

   proof ↗⚑ flag

   Fastmail—none0/10

   No evidence anywhere in the pack of AI-drafted replies, tone/voice matching, or generative reply features; Fastmail's evidence covers JMAP API, templates, filters, and general email management, not AI drafting.

   ⚑ flag

Ai triage

1. ai-native userAI triages my inbox for me — auto-labeling, categorizing, and surfacing what needs attention — with behavior I can steer and audit

   weight 3 · round to Zero
   Zero~partialprobed6/10

   Community and docs evidence show Zero markets itself as an AI-powered inbox that auto-categorizes emails, and its MCP server exposes tools to modify/create labels, filter/search by label, and answer questions about threads/mailbox content, giving a steerable interface for AI actions. However, there's no explicit documentation of automatic prioritization/surfacing of 'what needs attention' or an audit log of AI triage decisions beyond the generic MCP action list. Missing for 10: dedicated 'needs attention' surfacing/prioritization feature, explicit audit trail or history of AI-taken triage actions, and independent hands-on verification of auto-labeling accuracy.

   • [community] “Zero founder describes it as an AI-powered email client that auto-categorizes, summarizes threads, drafts replies, and lets users chat with …”
   • [claimed-docs] “Modify email labels”
   • [claimed-docs] “Create new custom labels with custom colors”
   • [claimed-docs] “Search emails with custom queries - Filter emails by labels”
   • [claimed-docs] “Ask questions about mailbox content - Ask questions about specific email threads”
   • [probe] “PROBE runtime (recorded 2026-09-06): a keyless shallow git clone of Mail-0/Zero landed a REAL self-hostable source tree — repo-root MCP.md (…”

   proof ↗⚑ flag

   Fastmail—none0/10

   Evidence covers Fastmail's rule-based Filters & Rules, search, and JMAP API access, but there is no mention of AI-driven triage, auto-labeling, categorization, or a steerable/auditable AI assistant surfacing important emails. Absence of evidence for this applicable capability means it does not deliver the story.

   • [claimed-docs] “Filters & Rules”
   • [claimed-docs] “Filters & Rules – Fastmail”
   • [claimed-docs] “Searching your mail”

   proof ↗⚑ flag

1. ai-native userPerform bulk operations across many items at once

   weight 2 · round drawn
   Zero~partialprobed5/10

   Zero's MCP server exposes email actions like 'Bulk delete emails' and 'Bulk archive emails' explicitly labeled as bulk operations, plus label/search operations that could apply across many items. However, evidence does not specify limits, batch size, or confirm bulk semantics beyond these two named actions, nor is there hands-on confirmation of bulk behavior at scale. missing for 10: independent/hands-on verification of bulk operations at scale, documentation of batch limits or performance, evidence of bulk operations beyond delete/archive (e.g., bulk label/move/send).

   • [claimed-docs] “Bulk delete emails - Bulk archive emails”
   • [claimed-docs] “Get email threads by ID - List emails in specific folders - Create and send new emails - Create email drafts - Send existing drafts - Delete…”
   • [probe] “PROBE runtime (recorded 2026-09-06): a keyless shallow git clone of Mail-0/Zero landed a REAL self-hostable source tree — repo-root MCP.md (…”

   proof ↗⚑ flag

   Fastmail~partialclaimed5/10

   JMAP's design (single HTTP request with a `methodCalls` array for query/fetch/send, fastmail-docs-38) inherently supports batching many operations together, and filters/rules (fastmail-docs-6) allow rule-based bulk processing of mail. However, there's no explicit documentation of a bulk-update/bulk-delete API pattern, no example of bulk operations across large item sets, and no independent evidence of this being used for AI-native bulk workflows. Missing for 10: explicit bulk operation API examples (e.g., bulk delete/move across many message IDs), documented limits/performance for large batches, and independent confirmation of successful bulk automation use.

   • [claimed-docs] “POST a `methodCalls` array. Query, fetch, and send, all in one HTTP request.”
   • [claimed-docs] “Filters & Rules”
   • [claimed-docs] “Sync changes more easily, more efficiently, and much, much faster. A single HTTP roundtrip is often all that's required.”

   proof ↗⚑ flag

2. ai-native userDefine rules that trigger actions automatically on events

   weight 3 · round to Fastmail
   Zero—none0/10

   Evidence shows Zero as an AI email client with MCP tool actions (search, compose, label, etc.) but no documented rule-based automation engine that triggers actions on events (e.g., 'when email arrives from X, do Y'). All actions appear to be user- or agent-invoked rather than event-triggered automation. Missing for full credit: any documented trigger/condition/action rules engine or scheduled/event-based automation feature.

   • [claimed-docs] “Modify email labels”
   • [claimed-docs] “Get email threads by ID - List emails in specific folders - Create and send new emails - Create email drafts - Send existing drafts - Delete…”
   • [claimed-docs] “Compose emails with AI assistance - Ask questions about mailbox content - Ask questions about specific email threads - Web search using Perp…”
   • [probe] “PROBE runtime (recorded 2026-09-06): a keyless shallow git clone of Mail-0/Zero landed a REAL self-hostable source tree — repo-root MCP.md (…”

   proof ↗⚑ flag

   Fastmail~partialcommunity5/10

   Fastmail's Filters & Rules feature lets users define rule-based automations (e.g., move/tag/forward on incoming mail conditions), which satisfies a basic version of 'rules trigger actions on events.' However, this is a traditional email-filter system, not framed for AI-native/agentic use, and there's no evidence of programmatic rule creation via API/JMAP, webhook-triggered actions, or AI-specific automation hooks beyond generic push/EventSource notifications. Missing for 10: API-driven rule creation/management, AI-agent-specific triggers or actions, and richer automation beyond mail filtering.

   • [claimed-docs] “Filters & Rules”
   • [claimed-docs] “Filters & Rules – Fastmail”
   • [claimed-docs] “Get instant push via EventSource — one connection, all mailboxes. Or use WebPush for mobile-compatible push, no permanent connection require…”
   • [community] “Fastmail has an easy migration tool as well if you don't want to go the IMAP route. Now, migrating filters and rules over on the other hand.…”

   proof ↗⚑ flag

3. ai-native userSchedule recurring jobs or workflows

   weight 2 · round drawn
   Zero—none0/10

   Zero is an AI email client with MCP tools for email actions (labels, search, compose, AI Q&A) but no evidence of scheduling recurring jobs or workflows/automation triggers.

   ⚑ flag

   Fastmail—none0/10

   No evidence of scheduling recurring jobs/workflows; only email-specific automation like Filters & Rules, Scheduled Send (one-time), and Snooze are documented, none of which support recurring automated workflows or job scheduling via API/JMAP. missing for 10: recurring job/workflow scheduler, cron-like automation, evidence of JMAP being used to trigger scheduled/recurring tasks.

   • [claimed-docs] “Filters & Rules”
   • [claimed-docs] “Scheduled Send”
   • [claimed-docs] “Snooze messages to just when you need them. Whether it’s tickets to that stadium gig in September, or a bill due next Thursday, sometimes yo…”

   proof ↗⚑ flag

Calendar

1. power-userSee my calendar, respond to invites, and create events without leaving the email client

   weight 2 · round to Fastmail
   Zero—none0/10

   The axis applies to this product kind (peer products hold positive or none verdicts on this story), so lack of evidence for an applicable capability is "none", never "na". (na/none harmonized at arena bring-up — see pipeline/scripts/na-harmonize.ts.)

   ⚑ flag

   Fastmail✓fullclaimed7/10

   Fastmail's docs confirm built-in Calendar with event and invitation handling directly in the mail/webmail client (fastmail-docs-14/34), and JMAP supports calendar via CalDAV replacement (fastmail-docs-42), consistent with an integrated calendar app alongside email. However, evidence lacks hands-on/community confirmation of the invite-response and event-creation UX specifically. Missing for 10: independent/community corroboration of calendar RSVP and event-creation workflow, and detail on UI integration depth.

   • [claimed-docs] “Calendar events and invitations”
   • [claimed-docs] “Calendar events and invitations – Fastmail”
   • [claimed-docs] “JMAP is the open protocol that replaces IMAP (and CardDAV and CalDAV). It's faster, simpler, more powerful, and built for how email works to…”

   proof ↗⚑ flag

2. power-userShare my availability or insert bookable meeting times directly into an email

   weight 1 · round drawn
   Zero—none0/10

   Zero is an email client with AI/MCP features for composing, searching, and managing emails, but no evidence in the pack mentions calendar integration, availability sharing, or inserting bookable meeting times into emails.

   ⚑ flag

   Fastmail—none0/10

   The evidence only shows generic 'Calendar events and invitations' documentation (RSVP/invite handling) with no mention of an availability-sharing or booking-link feature akin to scheduling assistants; no docs or community reports describe inserting bookable meeting slots into emails.

   • [claimed-docs] “Calendar events and invitations”
   • [claimed-docs] “Calendar events and invitations – Fastmail”

   proof ↗⚑ flag

Sending

1. power-userSee whether and when recipients opened my email

   weight 1 · round drawn
   Zero—none0/10

   No evidence anywhere in the pack mentions read receipts, open tracking, or notifications about when recipients open emails; the MCP/docs only cover sending, drafting, labeling, and searching emails.

   ⚑ flag

   Fastmail—none0/10

   No evidence in the pack mentions read receipts, delivery/open tracking, or any similar feature in Fastmail's composing/sending tools or documentation.

   ⚑ flag

2. power-userSchedule an email to send later and undo a send within a grace window

   weight 2 · round to Fastmail
   Zero—none0/10

   No evidence anywhere in the pack mentions scheduled send or undo-send functionality; MCP docs list send/draft/delete but nothing about delayed sending or a grace-window recall.

   • [claimed-docs] “Get email threads by ID - List emails in specific folders - Create and send new emails - Create email drafts - Send existing drafts - Delete…”
   • [claimed-docs] “Get email threads by ID - List emails in specific folders - Create and send new emails - Create email drafts - Send existing drafts”

   proof ↗⚑ flag

   Fastmail✓fullclaimed8/10

   Fastmail has dedicated first-party docs for both 'Scheduled Send' and 'Undo send' features, directly matching the story's requirements. Missing for 10: independent/hands-on corroboration of the undo grace-window mechanics or scheduling UX details beyond doc titles.

   • [claimed-docs] “Scheduled Send”
   • [claimed-docs] “Undo send”
   • [claimed-docs] “Scheduled Send – Fastmail”
   • [claimed-docs] “Undo send – Fastmail”

   proof ↗⚑ flag

Templates

1. power-userInsert saved snippets or templates — with variables and attachments — instead of retyping the same reply

   weight 2 · round to Fastmail
   Zero—none0/10

   No evidence pack item mentions saved snippets, canned responses, or templates with variables/attachments; the docs describe AI-assisted composing, MCP tools, labels, and self-hosting but nothing about a snippet/template insertion feature.

   ⚑ flag

   Fastmail~partialclaimed4/10

   Fastmail documents a dedicated "Templates" feature for saved replies, supporting the core ask of inserting canned text instead of retyping, but the evidence pack gives only the article title with no detail on variable substitution or attachment inclusion. missing for 10: documentation confirming template variables (e.g. name/date placeholders), attachment support within templates, and any independent/hands-on confirmation of these specifics.

   • [claimed-docs] “Templates”
   • [claimed-docs] “Templates – Fastmail”

   proof ↗⚑ flag

Offline

1. power-userRead, search, and write email offline, with changes syncing when I reconnect

   weight 2 · round to Fastmail
   Zero—none0/10

   No evidence anywhere in the pack mentions offline mode, local caching, or sync-on-reconnect; Zero appears to be a web-based email client requiring live connection to providers/AI services, with no offline-capability documentation.

   ⚑ flag

   Fastmail~partialclaimed6/10

   Fastmail has a dedicated 'Offline support' help article and a documented behavior detail (snoozed messages only reappear once back online, implying local caching + resync), which supports reading/writing offline with sync on reconnect. However, the evidence pack only gives titles/snippets, not confirmation that full-text search works offline or exactly how conflict resolution/sync works, and there's no independent hands-on test confirming offline compose/search reliability. Missing for 10: detailed doc content on offline search, independent verification of offline write/compose queuing and reconnection sync behavior, and confirmation across web/mobile clients.

   • [claimed-docs] “Offline support”
   • [claimed-docs] “Offline support – Fastmail”
   • [claimed-docs] “If you're offline when a snoozed message is scheduled to return to your Inbox, you will not see the snoozed message reappear until you're ba…”
   • [claimed-docs] “Sync changes more easily, more efficiently, and much, much faster. A single HTTP roundtrip is often all that's required.”

   proof ↗⚑ flag

1. ai-native userDo everything through the API that I can do in the UI

   weight 2 · round to Zero
   Zero~partialprobed6/10

   Zero's MCP server exposes many core email actions (search, send, draft, delete, labels, AI compose, thread Q&A) that mirror UI functionality, giving strong API-parity for mail operations. However missing for 10: no evidence of API parity for UI-specific settings like customizable keyboard shortcuts, UI theming/customization, unified inbox provider management, or account/connection setup via API — these remain UI-only per docs, and there's no independent confirmation the MCP surface is fully comprehensive versus a curated subset.

   • [claimed-docs] “Compose emails with AI assistance”
   • [claimed-docs] “Ask questions about specific email threads”
   • [claimed-docs] “Search emails with custom queries - Filter emails by labels”
   • [claimed-docs] “Ask questions about mailbox content - Ask questions about specific email threads”
   • [claimed-docs] “Get email threads by ID - List emails in specific folders - Create and send new emails - Create email drafts - Send existing drafts - Delete…”
   • [claimed-docs] “Get all user labels - Create new custom labels with custom colors - Delete existing labels”
   • [claimed-docs] “Compose emails with AI assistance - Ask questions about mailbox content - Ask questions about specific email threads - Web search using Perp…”
   • [probe] “PROBE runtime (recorded 2026-09-06): a keyless shallow git clone of Mail-0/Zero landed a REAL self-hostable source tree — repo-root MCP.md (…”
   • [claimed-docs] “Customizable keyboard shortcuts”
   • [github] “Customizable UI & Features – Tailor your email experience the way you want it.”

   proof ↗⚑ flag

   Fastmail~partialclaimed5/10

   Fastmail's JMAP API is well-documented for core mail operations (session discovery, OAuth, push via EventSource, single-roundtrip method calls) and JMAP also natively covers contacts/calendar, giving broad coverage beyond typical webmail APIs. However, the evidence never confirms API parity for many UI-only features referenced in docs (masked email management, snooze, templates, filters/rules configuration, scheduled send) — these are documented as UI/help features without corresponding API examples. missing for 10: explicit API endpoints/examples for masked email, snooze, filters, templates, scheduled send parity; independent developer confirmation that all UI actions are API-reachable.

   • [claimed-docs] “Fetch `/.well-known/jmap` for the session object - capabilities, accounts, and all API URLs.”
   • [claimed-docs] “Sync changes more easily, more efficiently, and much, much faster. A single HTTP roundtrip is often all that's required.”
   • [claimed-docs] “POST a `methodCalls` array. Query, fetch, and send, all in one HTTP request.”
   • [claimed-docs] “API Documentation”
   • [claimed-docs] “Masked Email”
   • [claimed-docs] “Filters & Rules”
   • [claimed-docs] “Snooze messages to just when you need them. Whether it’s tickets to that stadium gig in September, or a bill due next Thursday, sometimes yo…”

   proof ↗⚑ flag

2. ai-native userExport all of my data in open formats and leave

   weight 3 · round to Fastmail
   Zero—none0/10

   Evidence shows Zero is self-hostable, open-source, and doesn't sell user data, plus a Drizzle Studio DB viewer for self-hosters, but there is no documented data-export feature (e.g., mbox/EML export, takeout tool) letting a user extract all their mail data in an open format and leave the service.

   • [github] “gives users the power to **self-host** their own email app”
   • [github] “gives users the power to self-host their own email app while also integrating external services like Gmail and other email providers”
   • [github] “Zero does not track, collect, or sell your data in any way.”
   • [claimed-docs] “View and edit data with Drizzle Studio pnpm db:studio”

   proof ↗⚑ flag

   Fastmail~partialclaimed4/10

   Fastmail's evidence shows JMAP is an open, non-proprietary standard with full API access (session object, method calls, OAuth tokens) that could in principle be used to pull out all mail data, and there's a dedicated 'Open source and standards' page, but there is no explicit documentation of a one-click full data export/backup feature (mail+contacts+calendar) for leaving the service — only 'Import your mail' guidance is evidenced. missing for 10: documented full-account export/backup tool covering mail, contacts, and calendar; explicit data-portability/GDPR export docs; independent confirmation of successful full export.

   • [claimed-docs] “JMAP is an open standard any organisation can implement, not more proprietary lock-in from big tech companies.”
   • [claimed-docs] “Open source and standards | Fastmail”
   • [claimed-docs] “Fetch `/.well-known/jmap` for the session object - capabilities, accounts, and all API URLs.”
   • [claimed-docs] “API Documentation”
   • [claimed-docs] “Import your mail”

   proof ↗⚑ flag

3. ai-native userRead the product's source under an open license

   weight 2 · round to Zero
   Zero✓fullprobed8/10

   Zero's source is publicly hosted on GitHub (Mail-0/Zero) with a full contributing guide, self-hosting instructions, and a verified runtime probe confirming a real, clonable source tree with Docker configs for self-hosting — consistent with an open-source project freely readable by AI-native users. Missing for 10: explicit citation of the license file/name (e.g. MIT/AGPL) to confirm licensing terms.

   • [github] “Self-Hosting Freedom – Run your own email app with ease.”
   • [github] “gives users the power to **self-host** their own email app”
   • [github] “gives users the power to self-host their own email app while also integrating external services like Gmail and other email providers”
   • [claimed-docs] “View and edit data with Drizzle Studio pnpm db:studio”
   • [probe] “PROBE runtime (recorded 2026-09-06): a keyless shallow git clone of Mail-0/Zero landed a REAL self-hostable source tree — repo-root MCP.md (…”

   proof ↗⚑ flag

   Fastmail—none0/10

   Fastmail is a proprietary commercial email service; while it supports open standards like JMAP and has a page titled 'Open source and standards' (fastmail-docs-23), there is no evidence that Fastmail's own product source code is published under an open license for users/AI agents to read.

   • [claimed-docs] “Open source and standards | Fastmail”
   • [claimed-docs] “JMAP is an open standard any organisation can implement, not more proprietary lock-in from big tech companies.”

   proof ↗⚑ flag

4. ai-native userSelf-host the core product

   weight 3 · round to Zero
   Zero✓fullprobed8/10

   Multiple GitHub and docs citations explicitly advertise 'Self-Hosting Freedom' and describe running your own email app, and a runtime probe confirms a real self-hostable source tree with docker-compose files for self-hosting deployment. Missing for 10: independent hands-on report of a completed self-host deployment beyond the repo/docker-compose evidence, and more detailed self-host setup documentation.

   • [github] “Self-Hosting Freedom – Run your own email app with ease.”
   • [github] “⚙️ Self-Hosting Freedom – Run your own email app with ease.”
   • [github] “gives users the power to **self-host** their own email app”
   • [github] “⚙️ **Self-Hosting Freedom** – Run your own email app with ease.”
   • [github] “gives users the power to self-host their own email app while also integrating external services like Gmail and other email providers”
   • [claimed-docs] “Self-hosting capabilities”
   • [probe] “PROBE runtime (recorded 2026-09-06): a keyless shallow git clone of Mail-0/Zero landed a REAL self-hostable source tree — repo-root MCP.md (…”

   proof ↗⚑ flag

   Fastmail—none0/10

   The axis applies to this product kind (peer products hold positive or none verdicts on this story), so lack of evidence for an applicable capability is "none", never "na". (na/none harmonized at arena bring-up — see pipeline/scripts/na-harmonize.ts.)

   ⚑ flag

1. ai-native userChoose where my data is stored (region/residency)

   weight 2 · round to Zero
   Zero~partialclaimed5/10

   Zero's self-hosting capability (own infra, own database via docker-compose) lets a user effectively choose where their data lives, and it claims not to track/collect/sell data, but there is no explicit region/residency selection feature or documented multi-region hosted offering. missing for 10: explicit region/residency selection UI or hosted multi-region options, documentation on data locality guarantees for the hosted SaaS version, independent confirmation of self-host deployment satisfying residency requirements.

   • [github] “Self-Hosting Freedom – Run your own email app with ease.”
   • [github] “⚙️ Self-Hosting Freedom – Run your own email app with ease.”
   • [github] “gives users the power to **self-host** their own email app”
   • [github] “⚙️ **Self-Hosting Freedom** – Run your own email app with ease.”
   • [claimed-docs] “Self-hosting capabilities”
   • [github] “gives users the power to self-host their own email app while also integrating external services like Gmail and other email providers”
   • [github] “Zero does not track, collect, or sell your data in any way.”

   proof ↗⚑ flag

   Fastmail—none0/10

   The evidence pack contains no mention of data residency, regional storage options, or where Fastmail's servers/data centers are located; nothing addresses letting users choose a storage region. missing for 10: any documentation of regional data residency options, data center locations, or user controls for choosing where data is stored.

   ⚑ flag

2. ai-native userPrevent my data from being used to train AI models

   weight 3 · round to Zero
   Zero~partialclaimed5/10

   Zero states it does not track, collect, or sell user data, and self-hosting is available which would let users fully control data flow, implying no AI training on user data. However, there is no explicit statement or policy about AI-model training exclusion (e.g., no clause addressing whether email content sent to AI features like compose/summarize is used for model training). missing for 10: explicit AI-training opt-out/data-use policy, third-party AI provider data-handling terms, independent verification of the no-training claim.

   • [github] “Zero does not track, collect, or sell your data in any way.”
   • [github] “gives users the power to **self-host** their own email app”
   • [github] “gives users the power to self-host their own email app while also integrating external services like Gmail and other email providers”

   proof ↗⚑ flag

   Fastmail—none0/10

   No evidence in the pack addresses AI training data usage, opt-out controls, or any explicit privacy commitment regarding AI model training on user email data. missing for 10: any AI-training data policy, opt-out mechanism, or explicit statement that user data is not used to train AI models.

   ⚑ flag

3. ai-native userControl data retention and deletion

   weight 2 · round to Zero
   Zero~partialclaimed5/10

   Zero claims a no-tracking/no-sell data policy and supports self-hosting (giving users full control over their own data and deletion since they own the infrastructure), plus MCP tools include explicit 'delete emails' actions. However, there's no documented data retention policy, no explicit account/data deletion workflow or export tooling described, and no independent verification of the no-tracking claim. missing for 10: documented retention/export/deletion policy for hosted use, independent audit of data practices, explicit account-deletion or right-to-be-forgotten flow.

   • [github] “Zero does not track, collect, or sell your data in any way.”
   • [github] “gives users the power to **self-host** their own email app”
   • [github] “gives users the power to self-host their own email app while also integrating external services like Gmail and other email providers”
   • [claimed-docs] “Get email threads by ID - List emails in specific folders - Create and send new emails - Create email drafts - Send existing drafts - Delete…”
   • [claimed-docs] “Bulk delete emails - Bulk archive emails”

   proof ↗⚑ flag

   Fastmail—none0/10

   No evidence pack items address data retention policies, account deletion, data export/erasure controls, or AI-specific data handling for training/processing. The pack covers JMAP API, features, and general reviews but nothing on retention/deletion controls.

   ⚑ flag

4. ai-native userOpt out of telemetry and usage tracking

   weight 2 · round to Zero
   Zero~partialprobed5/10

   Zero's GitHub page states it 'does not track, collect, or sell your data in any way,' and self-hosting support (Docker compose files, self-hosting docs) lets AI-native users run their own instance with no vendor telemetry at all. However there is no explicit telemetry settings/opt-out toggle documented, no privacy policy detail, and no independent verification of the no-tracking claim. Missing for 10: explicit telemetry opt-out control/setting, detailed privacy policy, and independent/hands-on confirmation of the no-tracking claim.

   • [github] “Zero does not track, collect, or sell your data in any way.”
   • [github] “Self-Hosting Freedom – Run your own email app with ease.”
   • [github] “⚙️ Self-Hosting Freedom – Run your own email app with ease.”
   • [probe] “PROBE runtime (recorded 2026-09-06): a keyless shallow git clone of Mail-0/Zero landed a REAL self-hostable source tree — repo-root MCP.md (…”

   proof ↗⚑ flag

   Fastmail—none0/10

   No evidence pack item discusses telemetry, usage tracking, analytics opt-out, or any privacy settings specific to AI-native data collection controls; the docs focus on JMAP/API features and general email functionality.

   ⚑ flag

Protection

1. switcherUse aliases or masked addresses so sign-ups and strangers never learn my real address

   weight 1 · round to Fastmail
   Zero—none0/10

   Zero is an AI-powered unified email client with labels, search, and MCP integrations, but nothing in the evidence pack describes email alias generation or masked/burner address creation to hide a user's real address from sign-ups or strangers.

   ⚑ flag

   Fastmail✓fullcommunity8/10

   Fastmail's Masked Email feature (fastmail-docs-18/29) directly delivers per-signup masked addresses so real address stays hidden, plus separate alias setup docs (fastmail-docs-12/36), and community testimony confirms real-world use for throwaway/sketchy sites (fastmail-comm-1). missing for 10: independent hands-on verification of masked-email creation flow beyond docs and a single community mention, and no detail on limits/edge cases of masked addresses.

   • [claimed-docs] “Masked Email”
   • [claimed-docs] “Masked Email – Fastmail”
   • [claimed-docs] “How to set up aliases”
   • [claimed-docs] “How to set up aliases – Fastmail”
   • [community] “Fastmail is fantastic, I've been a very happy customer for at least a couple years now. Masked emails have been so nice for throwaway/sketch…”

   proof ↗⚑ flag

2. switcherThe client protects me from senders' tracking — blocking read pixels by default — and is transparent about what it does with my mail data

   weight 2 · round to Zero
   Zero~partialclaimed3/10

   Only a general privacy claim ('Zero does not track, collect, or sell your data in any way') is evidenced, with no mention of read-pixel/tracking-pixel blocking specifically or a detailed data-handling policy. missing for 10: explicit read-receipt/tracking-pixel blocking feature, documentation of default-on behavior, a privacy policy detailing mail data handling, and independent confirmation of the no-tracking claim.

   • [github] “Zero does not track, collect, or sell your data in any way.”

   proof ↗⚑ flag

   Fastmail—none0/10

   No evidence in the pack mentions blocking tracking pixels/read receipts, image proxying, or any specific transparency documentation about mail data handling; general privacy sentiment from community comments (fastmail-comm-3) is too vague to establish this specific capability.

   ⚑ flag

Migration

1. switcherImport my complete mail history and contacts from my old provider or client

   weight 1 · round to Fastmail
   Zero—none0/10

   Zero connects to providers like Gmail/Outlook for unified inbox access, but no evidence describes any import/migration tool for bulk historical mail or contacts from an old provider/client — no mention of mbox/EML import, contact list import, or migration wizard.

   ⚑ flag

   Fastmail~partialcommunity6/10

   Fastmail has a documented 'Import your mail' tool plus IMAP fetch/forwarding options for migrating mail from other providers, and community reports confirm an easy migration tool and IMAP-based fetching from Gmail. However, evidence does not clearly cover contacts import, and community feedback flags that filters/rules migration is notably harder ('migrating filters and rules over on the other hand...'). Missing for 10: explicit contacts-import documentation, confirmation of complete mail history fidelity, and stronger independent verification of a smooth full-history+contacts migration.

   • [claimed-docs] “Import your mail”
   • [claimed-docs] “Import your mail – Fastmail”
   • [community] “As an alternative to forwarding, you can also configure Fastmail to fetch mail from (and send via) Gmail like a mail client.”
   • [community] “Fastmail has an easy migration tool as well if you don't want to go the IMAP route. Now, migrating filters and rules over on the other hand.…”
   • [claimed-docs] “Move from Gmail”

   proof ↗⚑ flag

Search

1. power-userSearch is fast and precise — operators, filters, and ranked results across my full mail history

   weight 2 · round to Zero
   Zero~partialcommunity4/10

   Evidence shows a basic 'search emails with custom queries' and 'filter by labels' capability via the MCP server, but there is no documentation of advanced operators, ranked relevance, or performance/scale across full mail history; a community comment even flags missing basic navigation features, suggesting search UX is still immature. missing for 10: documented search operators/syntax, evidence of ranking/relevance across full historical mail, performance benchmarks, independent hands-on confirmation of search speed/precision.

   • [claimed-docs] “Search emails with custom queries - Filter emails by labels”
   • [community] “hoping to see some more discussion here - i'd love to replace superhuman. However, until Zero has real keyboard navigation, i'll have to wai…”
   • [claimed-docs] “Compose emails with AI assistance - Ask questions about mailbox content - Ask questions about specific email threads - Web search using Perp…”

   proof ↗⚑ flag

   Fastmail~partialclaimed3/10

   Fastmail has a dedicated 'Searching your mail' help article confirming search is a first-class feature, and JMAP's fast query/fetch model implies backend efficiency, but the evidence pack never details actual search operators, filter syntax, ranking behavior, or performance across full mail history. missing for 10: documented search operator syntax (from:, subject:, has:attachment etc.), evidence of ranked/relevance-based results, benchmarks or user reports on search speed across large mail archives, independent corroboration of search precision.

   • [claimed-docs] “Searching your mail”
   • [claimed-docs] “Searching your mail – Fastmail”
   • [claimed-docs] “Sync changes more easily, more efficiently, and much, much faster. A single HTTP roundtrip is often all that's required.”
   • [claimed-docs] “POST a `methodCalls` array. Query, fetch, and send, all in one HTTP request.”

   proof ↗⚑ flag

Shortcuts

1. power-userDo everything from the keyboard — comprehensive shortcuts and a command palette — in an interface fast enough to never make me wait

   weight 3 · round to Fastmail
   Zero!disputedcontradicted2/10

   Zero's own roadmap lists 'customizable keyboard shortcuts' as a planned (not yet shipped) feature, and a hands-on community comment explicitly states the product lacks 'real keyboard navigation' today, directly contradicting any power-user keyboard-first claim; no command palette is mentioned anywhere in the evidence. missing for 10: shipped keyboard shortcut system, command palette, any evidence of interface speed/responsiveness for power users.

   • [claimed-docs] “Customizable keyboard shortcuts”
   • [community] “hoping to see some more discussion here - i'd love to replace superhuman. However, until Zero has real keyboard navigation, i'll have to wai…”

   proof ↗⚑ flag

   Fastmail~partialcommunity5/10

   Fastmail documents a dedicated keyboard shortcuts feature and JMAP-based sync architecture emphasizing speed, and community feedback corroborates the interface being notably fast ('a ton faster' than alternatives). However, there is no evidence of a command palette or comprehensive shortcut coverage claims, and no hands-on confirmation of full keyboard-only operation. Missing for 10: explicit command-palette feature, evidence of exhaustive/comprehensive shortcut coverage beyond a single help article, independent benchmarking of UI responsiveness under load.

   • [claimed-docs] “Keyboard shortcuts”
   • [claimed-docs] “Keyboard shortcuts – Fastmail”
   • [claimed-docs] “Sync changes more easily, more efficiently, and much, much faster. A single HTTP roundtrip is often all that's required.”
   • [community] “I switched from protonmail to fastmail recently. Fastmail was a ton faster and didn't randomly forget my sessions. Night and day to use. It …”
   • [community] “I recently moved my email to FastMail and I really like it. I even prefer its web interface over Gmail's.”

   proof ↗⚑ flag

Channels

1. team-leadThe same inbox also handles adjacent customer channels — SMS, WhatsApp, social, or live chat — beside email

   weight 1 · round drawn
   Zero—none0/10

   The axis applies to this product kind (peer products hold positive or none verdicts on this story), so lack of evidence for an applicable capability is "none", never "na". (na/none harmonized at arena bring-up — see pipeline/scripts/na-harmonize.ts.)

   ⚑ flag

   Fastmail—none0/10

   The axis applies to this product kind (peer products hold positive or none verdicts on this story), so lack of evidence for an applicable capability is "none", never "na". (na/none harmonized at arena bring-up — see pipeline/scripts/na-harmonize.ts.)

   ⚑ flag

Routing

1. team-leadAssign conversations to teammates and route incoming mail with rules so ownership is explicit

   weight 2 · round to Fastmail
   Zero—none0/10

   Zero is a personal AI-powered email client with unified inbox, labels, and MCP tooling, but no evidence anywhere in the pack describes team features like assigning conversations to teammates or configuring routing/ownership rules — capabilities relevant for shared team inboxes. This is a fair axis for an email client, but no evidence supports it, so it's 'none' rather than 'na'.

   ⚑ flag

   Fastmail~partialclaimed3/10

   Fastmail's docs confirm mail routing via Filters & Rules, which lets a team-lead direct incoming mail to specific folders/addresses, but there is no evidence of any conversation-assignment feature (assigning a thread to a specific teammate with ownership tracking) anywhere in the pack. Missing for 10: conversation/ticket assignment to teammates, ownership/status indicators, any shared-inbox collaboration UI beyond basic filters.

   • [claimed-docs] “Filters & Rules”
   • [claimed-docs] “Filters & Rules – Fastmail”

   proof ↗⚑ flag

Shared inbox

1. team-leadWe can discuss an email in an internal side-thread — comments and @mentions beside the message — instead of forwarding copies around

   weight 2 · round drawn
   Zero—none0/10

   Evidence covers email management, MCP AI features, and self-hosting, but nothing describes internal side-threads with comments/@mentions for team discussion of emails without forwarding.

   ⚑ flag

   Fastmail—none0/10

   No evidence of any internal comment/annotation or @mention feature attached to emails in Fastmail; evidence only covers standard email features (filters, search, aliases, JMAP protocol) and none mention side-thread discussion or team collaboration around a message.

   ⚑ flag

2. team-leadMy team works shared inboxes together — shared accounts or team channels where everyone sees the same conversation state

   weight 3 · round drawn
   Zero—none0/10

   Zero is positioned as a personal AI-powered unified inbox for individual users (Gmail/Outlook accounts), with no evidence of shared inboxes, team channels, or shared conversation state across multiple users; features described are individual email management, MCP tooling, and self-hosting, not multi-user collaboration.

   • [github] “Unified Inbox – Connect multiple email providers like Gmail, Outlook, and more.”
   • [community] “Zero founder describes it as an AI-powered email client that auto-categorizes, summarizes threads, drafts replies, and lets users chat with …”

   proof ↗⚑ flag

   Fastmail—none0/10

   Evidence covers JMAP protocol, personal productivity features, and multi-account login, but there is no mention of shared inboxes, team channels, or shared conversation state features for teams. Fastmail's docs reference 'Logging in to multiple accounts' which is about one user accessing several separate accounts, not shared team visibility into the same inbox.

   • [claimed-docs] “Logging in to multiple accounts”
   • [claimed-docs] “Logging in to multiple accounts – Fastmail”

   proof ↗⚑ flag

Followups

1. power-userSnooze conversations and set follow-up reminders that resurface a thread if nobody replies

   weight 2 · round to Fastmail
   Zero—none0/10

   No evidence anywhere in the pack mentions snooze, follow-up reminders, or resurfacing threads after no reply; the documented features cover labels, search, compose, AI Q&A, and self-hosting only.

   ⚑ flag

   Fastmail~partialclaimed5/10

   Fastmail's docs confirm a snooze feature that resurfaces messages at a chosen time, including behavior when offline, which covers the 'snooze conversations' half of the story. However there is no evidence of a 'nudge'/follow-up reminder that resurfaces a thread specifically if nobody replies — snoozing is time-based, not reply-tracking. missing for 10: evidence of a no-reply-triggered follow-up reminder feature, independent confirmation of snooze behavior beyond the offline-support note.

   • [claimed-docs] “Snooze messages to just when you need them. Whether it’s tickets to that stadium gig in September, or a bill due next Thursday, sometimes yo…”
   • [claimed-docs] “If you're offline when a snoozed message is scheduled to return to your Inbox, you will not see the snoozed message reappear until you're ba…”

   proof ↗⚑ flag

Inbox structure

1. power-userSelect many conversations at once and archive, label, or mark them done in one stroke

   weight 1 · round to Zero
   Zero~partialcommunity4/10

   Zero's MCP docs explicitly list 'Bulk delete emails' and 'Bulk archive emails' plus label modification tools, showing some bulk-action capability, but this is exposed via an AI/MCP tool interface rather than confirmed as a native UI multi-select action, and there's no mention of a 'mark done' state or how many items can be selected/acted on interactively. Community commentary even flags gaps in basic power-user UI ergonomics (no real keyboard navigation), suggesting bulk in-UI triage may be immature. missing for 10: confirmed UI multi-select archive/label/done action, evidence of a 'done' state, independent hands-on confirmation of bulk UI workflow.

   • [claimed-docs] “Modify email labels”
   • [claimed-docs] “Bulk delete emails - Bulk archive emails”
   • [claimed-docs] “Get all user labels - Create new custom labels with custom colors - Delete existing labels”
   • [community] “hoping to see some more discussion here - i'd love to replace superhuman. However, until Zero has real keyboard navigation, i'll have to wai…”

   proof ↗⚑ flag

   Fastmail~partialclaimed3/10

   Fastmail's documented Keyboard Shortcuts and Filters & Rules pages imply an interface that supports quick, multi-message actions, but no citation explicitly describes selecting multiple conversations for bulk archive/label/mark-done in one action. missing for 10: explicit documentation or hands-on evidence of multi-select checkboxes, bulk archive/label/mark-done actions, and confirmation of conversation-view group actions.

   • [claimed-docs] “Keyboard shortcuts”
   • [claimed-docs] “Keyboard shortcuts – Fastmail”
   • [claimed-docs] “Filters & Rules”
   • [claimed-docs] “Filters & Rules – Fastmail”

   proof ↗⚑ flag

2. power-userSplit my inbox into focused streams — important, team, newsletters, calendar invites — so triage happens in priority order, not arrival order

   weight 3 · round to Fastmail
   Zero—none0/10

   Evidence shows Zero supports labels, filtering, unified inbox, and AI Q&A, but there is no mention of dedicated inbox streams/views separating important, team, newsletter, and calendar-invite emails for priority-ordered triage. Labeling/filtering capabilities exist but no evidence of a stream-based triage UI or auto-categorized views as described in the story.

   • [claimed-docs] “Modify email labels”
   • [claimed-docs] “Search emails with custom queries - Filter emails by labels”
   • [claimed-docs] “Get all user labels - Create new custom labels with custom colors - Delete existing labels”
   • [community] “Zero founder describes it as an AI-powered email client that auto-categorizes, summarizes threads, drafts replies, and lets users chat with …”

   proof ↗⚑ flag

   Fastmail~partialclaimed5/10

   Fastmail's Filters & Rules can route mail (e.g. newsletters, calendar invites) into separate folders/labels, and saved searches let a power-user build custom views, giving a rough approximation of prioritized streams — but the evidence never shows a dedicated multi-pane/tabbed 'focused inbox' UI or explicit stream-based triage ordering like Gmail's Priority Inbox or Outlook's Focused Inbox. missing for 10: a documented feature for simultaneous multi-stream inbox views, automatic 'important' classification, and evidence of ordering triage by priority rather than by folder/search separately.

   • [claimed-docs] “Filters & Rules”
   • [claimed-docs] “Filters & Rules – Fastmail”
   • [claimed-docs] “Searching your mail”
   • [claimed-docs] “Searching your mail – Fastmail”
   • [claimed-docs] “Calendar events and invitations”
   • [claimed-docs] “Calendar events and invitations – Fastmail”

   proof ↗⚑ flag