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Rank #2 of 6 in Email Clients & Email AI

Zero logo

Zero Email Inc. (Mail-0 open-source project)

10.8k6.7k/yr +7

Showcase

Zero homepage screenshot
homepage · captured Sep 2026 · view live ↗

Try itExperimental

See what an agent can do with Zero before you ever sign up. Pick a story: recorded sessions replay real probe-harness transcripts; sandboxed self-drive sessions are designed and gated (docs/TRY-IT.md).

$git clone --depth 1 https://github.com/Mail-0/Zero.git /tmp/pa-zero # then list root files, MCP.md head, compose filesrecorded session — replayed, not live
recorded 2026-09-07 · exit 0 · captured verbatim by our probe harness, secrets redacted

Verified integrations

Connections to other tracked products — hover a chip for the verbatim evidence quote behind it.

By theme — the product's score on each story themeBy theme

Accounts openness — stories about accounts openness in this arenaAccounts opennessevidence →

Stories about accounts openness in this arena

17.7/100

Agenticness — how well agents can access and operate the productAgenticnessevidence →

How well agents can access and operate the product

30.6/100

Ai email — stories about ai email in this arenaAi emailevidence →

Stories about ai email in this arena

43.0/100

Automation depth — how much of the product can run unattendedAutomation depthevidence →

How much of the product can run unattended

8.6/100

Calendar integration — stories about calendar integration in this arenaCalendar integrationevidence →

Stories about calendar integration in this arena

0.0/100

Composing sending — stories about composing sending in this arenaComposing sendingevidence →

Stories about composing sending in this arena

0.0/100

Offline reliability — stories about offline reliability in this arenaOffline reliabilityevidence →

Stories about offline reliability in this arena

0.0/100

Openness — open source, data portability, and self-hosting storiesOpennessevidence →

Open source, data portability, and self-hosting stories

47.2/100

Privacy posture — data-handling and privacy storiesPrivacy postureevidence →

Data-handling and privacy stories

30.0/100

Privacy tracking — stories about privacy tracking in this arenaPrivacy trackingevidence →

Stories about privacy tracking in this arena

12.0/100

Search history — stories about search history in this arenaSearch historyevidence →

Stories about search history in this arena

16.0/100

Speed keyboard — stories about speed keyboard in this arenaSpeed keyboardevidence →

Stories about speed keyboard in this arena

6.0/100

Team collaboration — stories about team collaboration in this arenaTeam collaborationevidence →

Stories about team collaboration in this arena

0.0/100

Triage inbox — stories about triage inbox in this arenaTriage inboxevidence →

Stories about triage inbox in this arena

4.0/100

Story verdicts — every judged story with its evidenceStory verdicts

What’s free: 5 free · 0 paid · 0 enterprise · 18 not stated in evidence

?

Sorted by importance (agentic first) (high → low) · 54/54 stories · click a row’s chevron for the rationale and evidence

Connect an agent via an official MCP server G

Agent access

ai-native userAgenticness — how well agents can access and operate the productAgenticness3full8/10T

Delegate tasks to a built-in AI assistant inside the product G

Agentic features

ai-native userAgenticness — how well agents can access and operate the productAgenticness3full8/10T

Drive the product through a documented public API G

Agent access

ai-native userAgenticness — how well agents can access and operate the productAgenticness3full8/10T

Plug MCP servers into this product so it can use their tools G

Agent access

ai-native userAgenticness — how well agents can access and operate the productAgenticness3none0/10

Get AI-generated insights and suggestions from my data inside the product G

Agentic features

ai-native userAgenticness — how well agents can access and operate the productAgenticness2full7/10T

Operate the product with natural-language commands G

Agentic features

ai-native userAgenticness — how well agents can access and operate the productAgenticness2full7/10X

Point an agent at llms.txt or agent-oriented docs G

Agent access

ai-native userAgenticness — how well agents can access and operate the productAgenticness2partial6/10T

Build against official SDKs G

Agent access

ai-native userAgenticness — how well agents can access and operate the productAgenticness2partial5/10T

Issue scoped/least-privilege API credentials for an agent G

Agent access

ai-native userAgenticness — how well agents can access and operate the productAgenticness2none0/10

Use an official CLI G

Agent access

ai-native userAgenticness — how well agents can access and operate the productAgenticness2none0/10

Download a machine-readable API spec (OpenAPI or equivalent) G

Api quality

ai-native userAgenticness — how well agents can access and operate the productAgenticness2noneuntestednone yet

Explore an interactive API reference with runnable examples G

Api quality

ai-native userAgenticness — how well agents can access and operate the productAgenticness2noneuntestednone yet

Rely on versioned APIs with a documented deprecation policy G

Api quality

ai-native userAgenticness — how well agents can access and operate the productAgenticness2noneuntestednone yet

Run the product headlessly / in CI for automation G

Agent access

ai-native userAgenticness — how well agents can access and operate the productAgenticness2noneuntestednone yet

Set up automations that run autonomously in the background G

Agentic features

ai-native userAgenticness — how well agents can access and operate the productAgenticness2noneuntestednone yet

Subscribe to events via webhooks G

Agent access

ai-native userAgenticness — how well agents can access and operate the productAgenticness2noneuntestednone yet

Test against a sandbox environment without touching production data G

Api quality

ai-native userAgenticness — how well agents can access and operate the productAgenticness1noneuntestednone yet

Self-host the core product G

ai-native userOpenness — open source, data portability, and self-hosting storiesOpenness3fullfree8/10T

AI triages my inbox for me — auto-labeling, categorizing, and surfacing what needs attention — with behavior I can steer and audit C

Ai triage

ai-native userAi email — stories about ai email in this arenaAi email3partial6/10T

AI drafts replies in my own voice and tone — ready to review and send, not generic boilerplate C

Ai drafting

ai-native userAi email — stories about ai email in this arenaAi email3partial5/10X

Prevent my data from being used to train AI models G

ai-native userPrivacy posture — data-handling and privacy storiesPrivacy posture3partial5/10C

Connect several accounts across providers — Gmail, Microsoft 365, IMAP — and work them from one place C

Multi account

switcherAccounts openness — stories about accounts openness in this arenaAccounts openness3disputed4/10D

Do everything from the keyboard — comprehensive shortcuts and a command palette — in an interface fast enough to never make me wait C

Shortcuts

power-userSpeed keyboard — stories about speed keyboard in this arenaSpeed keyboard3disputed2/10D

Define rules that trigger actions automatically on events G

ai-native userAutomation depth — how much of the product can run unattendedAutomation depth3none0/10

Export all of my data in open formats and leave G

ai-native userOpenness — open source, data portability, and self-hosting storiesOpenness3none0/10

My team works shared inboxes together — shared accounts or team channels where everyone sees the same conversation state C

Shared inbox

team-leadTeam collaboration — stories about team collaboration in this arenaTeam collaboration3none0/10

Split my inbox into focused streams — important, team, newsletters, calendar invites — so triage happens in priority order, not arrival order C

Inbox structure

power-userTriage inbox — stories about triage inbox in this arenaTriage inbox3none0/10

An external agent — Claude, ChatGPT, or my own — can read, triage, draft, and send my email end to end through a documented connection C

Agent workflows

ai-native userAi email — stories about ai email in this arenaAi email2full8/10T

Read the product's source under an open license G

ai-native userOpenness — open source, data portability, and self-hosting storiesOpenness2fullfree8/10T

Ask an assistant questions across my whole inbox and calendar — who said what, what's outstanding — and get grounded answers C

Ai assistant

ai-native userAi email — stories about ai email in this arenaAi email2partial6/10T

Do everything through the API that I can do in the UI G

ai-native userOpenness — open source, data portability, and self-hosting storiesOpenness2partial6/10T

Choose where my data is stored (region/residency) G

ai-native userPrivacy posture — data-handling and privacy storiesPrivacy posture2partialfree5/10C

Control data retention and deletion G

ai-native userPrivacy posture — data-handling and privacy storiesPrivacy posture2partial5/10C

Opt out of telemetry and usage tracking G

ai-native userPrivacy posture — data-handling and privacy storiesPrivacy posture2partialfree5/10T

Perform bulk operations across many items at once G

ai-native userAutomation depth — how much of the product can run unattendedAutomation depth2partial5/10T

Search is fast and precise — operators, filters, and ranked results across my full mail history C

Search

power-userSearch history — stories about search history in this arenaSearch history2partial4/10X

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

Protection

switcherPrivacy tracking — stories about privacy tracking in this arenaPrivacy tracking2partial3/10C

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

Portability

switcherAccounts openness — stories about accounts openness in this arenaAccounts openness2none0/10

Schedule an email to send later and undo a send within a grace window C

Sending

power-userComposing sending — stories about composing sending in this arenaComposing sending2none0/10

Assign conversations to teammates and route incoming mail with rules so ownership is explicit C

Routing

team-leadTeam collaboration — stories about team collaboration in this arenaTeam collaboration2noneuntestednone yet

Insert saved snippets or templates — with variables and attachments — instead of retyping the same reply C

Templates

power-userComposing sending — stories about composing sending in this arenaComposing sending2noneuntestednone yet

Read, search, and write email offline, with changes syncing when I reconnect C

Offline

power-userOffline reliability — stories about offline reliability in this arenaOffline reliability2noneuntestednone yet

Schedule recurring jobs or workflows G

ai-native userAutomation depth — how much of the product can run unattendedAutomation depth2noneuntestednone yet

See my calendar, respond to invites, and create events without leaving the email client C

Calendar

power-userCalendar integration — stories about calendar integration in this arenaCalendar integration2noneuntestednone yet

Snooze conversations and set follow-up reminders that resurface a thread if nobody replies C

Followups

power-userTriage inbox — stories about triage inbox in this arenaTriage inbox2noneuntestednone yet

We can discuss an email in an internal side-thread — comments and @mentions beside the message — instead of forwarding copies around C

Shared inbox

team-leadTeam collaboration — stories about team collaboration in this arenaTeam collaboration2noneuntestednone yet

Self-host the email app and keep the mail pipeline under my own control C

Portability

switcherAccounts openness — stories about accounts openness in this arenaAccounts openness1fullfree7/10T

Select many conversations at once and archive, label, or mark them done in one stroke C

Inbox structure

power-userTriage inbox — stories about triage inbox in this arenaTriage inbox1partial4/10X

Import my complete mail history and contacts from my old provider or client C

Migration

switcherSearch history — stories about search history in this arenaSearch history1noneuntestednone yet

See whether and when recipients opened my email C

Sending

power-userComposing sending — stories about composing sending in this arenaComposing sending1noneuntestednone yet

Share my availability or insert bookable meeting times directly into an email C

Calendar

power-userCalendar integration — stories about calendar integration in this arenaCalendar integration1noneuntestednone yet

The same inbox also handles adjacent customer channels — SMS, WhatsApp, social, or live chat — beside email C

Channels

team-leadTeam collaboration — stories about team collaboration in this arenaTeam collaboration1noneuntestednone yet

Use aliases or masked addresses so sign-ups and strangers never learn my real address C

Protection

switcherPrivacy tracking — stories about privacy tracking in this arenaPrivacy tracking1noneuntestednone yet

Version, review, and roll back my automations G

ai-native userAutomation depth — how much of the product can run unattendedAutomation depth1n/auntestednone yet

Opportunities — the stories that would move this product's scores, from its own judged verdictsOpportunitiestop 8 of 42 stories with headroom

What would move Zero’s scores — derived from its own judged verdicts, biggest headroom first. Each line quotes what the judge found missing; shipping it (or evidencing it publicly) is the fix.

  1. Agenticness — how well agents can access and operate the productPlug MCP servers into this product so it can use their tools

    nonemoves agent-readyimpact 45

    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.

  2. Automation depth — how much of the product can run unattendedDefine rules that trigger actions automatically on events

    nonemoves PA Scoreimpact 30

    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').

  3. Openness — open source, data portability, and self-hosting storiesExport all of my data in open formats and leave

    nonemoves PA Scoreimpact 30

    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.

  4. Team collaboration — stories about team collaboration in this arenaMy team works shared inboxes together — shared accounts or team channels where everyone sees the same conversation state

    nonemoves PA Scoreimpact 30

    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.

  5. Triage inbox — stories about triage inbox in this arenaSplit my inbox into focused streams — important, team, newsletters, calendar invites — so triage happens in priority order, not arrival order

    nonemoves PA Scoreimpact 30

    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.

  6. Agenticness — how well agents can access and operate the productSet up automations that run autonomously in the background

    nonemoves Built-in AIimpact 30

    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.

  7. Agenticness — how well agents can access and operate the productRun the product headlessly / in CI for automation

    nonemoves agent-readyimpact 30

    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".

  8. Agenticness — how well agents can access and operate the productUse an official CLI

    nonemoves agent-readyimpact 30

    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.

Showing the top 8 of 42 — every none/partial verdict in the story verdicts table is headroom.

Think a verdict is wrong? Every verdicts-table row has a Flag link — see the methodology.

Coverage map — which docs area, API section, or community source covers which judged storiesCoverage map2 surfaces · 25 covered stories

Where the cited evidence behind each covered verdict came from — the same citations the verdicts table shows, no extra judging.

GitHub README25 stories

Probe proofs — replayable recordings from the probe harnessProbe proofs

Replayable recordings from our probe harness — see the Prove-It protocol to submit one.

$git clone --depth 1 https://github.com/Mail-0/Zero.git /tmp/pa-zero # then list root files, MCP.md head, compose filesreproduced
$ git clone --depth 1 https://github.com/Mail-0/Zero.git /tmp/pa-zero  # then list root files, MCP.md head, compose files
Cloning into '/tmp/pa-zero'...
--- root files ---
AGENT.md
LICENSE
MCP.md
README.md
ROADMAP.md
SECURITY.md
apps
crowdin.yml
docker
docker-compose.db.yaml
docker-compose.prod.yaml
eslint.config.mjs
i18n.json
i18n.lock
package.json
packages
--- MCP.md ---
### Zero MCP

## Capabilties
--- compose files ---
/tmp/pa-zero/docker-compose.db.yaml	/tmp/pa-zero/docker-compose.prod.yaml

Claims vs evidence — vendor claims reconciled against independent verdictsClaims vs evidence

9 of 11 testable claims verified · 2 contradictedintegrity 45/100

17 distinct capability claims found in Zero’s own claimed-docs/GitHub materials, reconciled against our judge’s independent verdicts.

9

Verified

0

Unverified

2

Contradicted

14

Undersold

Verified (11)
Contradicted (3)
Undersold (14)
Claims outside our story set (4)

Real capability claims found in Zero’s own materials, but no story in this arena’s taxonomy covers them yet — that’s feedback on the taxonomy, not a mark against the product.

  • Users can modify/change email labels on messages

    source ↗
  • Create, list, and delete custom labels with custom colors

    source ↗
  • AI assistant can perform web search via Perplexity AI to answer questions

    source ↗
  • UI and features can be customized to tailor the email experience

    source ↗
Suggest a story for these →

Business model

open-sourcefree-tiersubscription-flat

MIT-licensed and self-hostable, with a hosted app at 0.email offering a free tier and a paid Pro subscription for unlimited AI chat, auto-labeling, and writing assistance.

pricing ↗

Score trend

How this product’s scores have moved as evidence and verdicts are re-derived — a point per change, not per day.

PA Scoretracked since Sep 7 '26 — no movement recorded yet
Agent-readytracked since Sep 7 '26 — no movement recorded yet

Try Experimental

Run it in the microterminal →

Recorded agent sessions — and a live MCP handshake where the vendor ships one.

Flag

⚑ Flag a verdict

Think a verdict is wrong? Opens a prefilled GitHub issue — or use the ⚑ next to any verdict above.

Badge

Embed this product's score badge →

Hotlinked SVG — always shows the live current score.

For agents

Data