Category · Communication
Mailbox access APIs for AI agents
APIs that let an agent work in a mailbox a person already has. Searching and reading mail, writing drafts, sending and filing. The mailbox providers' own APIs and services that put one API over several providers. Compared on scopes, search, sync and send limits.
Capability keys mailbox.read · mailbox.search · mailbox.send · mailbox.drafts · mailbox.sync · All tools
letme.dev/mailbox.read picks the top-graded tool in this list and says how to call it direct; calling through letme comes later.
The same listing from the live API. Graded results come first, then the official MCP registry when no graded-only filter is set.
https://www.anchorterminal.com/api/v1/searchFilters
| Compare | # | Tool | Category | Grade | Score | Agent rating | p95 | Context | Price / x402 | Auth | Where | Details |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 11 | Nylas Email APINylas · HTTP API | Mailboxes | A | 78.7 | none | n/a | n/a | $15 / mo | OAuth or key | Hosted | ||
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Unified email API from Nylas for reading, searching, drafting and sending mail in a person's existing Gmail, Microsoft 365, Exchange, Yahoo, iCloud or IMAP mailbox, with webhooks for new mail. A hosted MCP server exposes the same data. Top strength One schema for messages, threads, drafts, folders and attachments across Gmail, Microsoft 365, Exchange EWS, Yahoo, iCloud and IMAP Top weakness Eight status incidents on email between 24 July and 17 September 2026, including about six hours of IMAP retrieval and webhook degradation on 10 September |
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| 16 | Gmail APIGoogle · HTTP API | Mailboxes | BB | 77.8 | none | n/a | n/a | Free | OAuth | Hosted | ||
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Google's REST API for Gmail mailboxes. It searches and reads messages and threads, writes drafts, sends mail, manages labels and settings, and reports mailbox changes through history records and Cloud Pub/Sub push notifications. Access is by OAuth 2.0. Top strength 14 OAuth scopes, with Top weakness Eight restricted scopes, including |
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| 97 | EmailEnginePostal Systems OÜ · HTTP API | Mailboxes | BB | 71.4 | none | n/a | n/a | $120.83 / mo | API key | Local | ||
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EmailEngine is self-hosted software from Postal Systems that puts one REST API over Gmail, Microsoft 365 and IMAP mailboxes, with webhooks for new mail and a beta MCP server. The owner runs it with Redis. Top strength Public OpenAPI 3.0 spec for version 2.82.2 with 82 operations, plus llms.txt on both sites and a capabilities.json manifest Top weakness Not open source. Running it beyond the 14-day trial needs a subscription at $1,450 or EUR 1,200 a year |
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| 197 | Outlook Mail (Microsoft Graph)Microsoft · HTTP API | Mailboxes | B | 66.3 | none | n/a | n/a | Your plan | OAuth | Hosted | ||
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Mail endpoints of Microsoft Graph for Outlook, Microsoft 365 and Exchange Online mailboxes. An app reads, searches, drafts, sends and files messages over REST with OAuth tokens from Microsoft Entra ID. Top strength Mail.ReadBasic reads messages without body, preview or attachments, and Mail.Send is separate from Mail.ReadWrite Top weakness sendMail has no idempotency key and answers 202 Accepted before delivery, so a retried send can go out twice |
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| 366 | UnipileUNIPILE SAS · HTTP API | Mailboxes | C | 58.4 | none | n/a | n/a | $55 / mo | API key | Hosted | ||
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Unipile is a hosted API from Unipile SAS in France that connects to accounts people already have. It reads, searches, sends and files mail in Gmail, Outlook and IMAP mailboxes, and also covers calendars, LinkedIn, WhatsApp, Instagram and Telegram. Top strength Public OpenAPI 3.0 spec with 94 operations, readable without a key, plus llms.txt and a Markdown copy of every docs page Top weakness A v1 access token reaches every connected account. Scoped keys, documented rate limits and |
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Nothing matches these filters. .
p95 latency and context cost come from our probes, which haven't run yet, so those columns start hidden. Grades run from AA to F, and agent-ready means BB or better. Filters, sorting and export run in your browser; the table is complete without JavaScript.
How we test this category
One test mailbox with the same two hundred messages on each provider. The same tasks run through each listing's API (search, read a thread, write a draft reply, send, label and archive, receive a new-mail event). We check scopes, sync delay and limits. In this run listings are graded from public evidence against the published checklist. This test hasn't run yet, so Task success is pending and the grades here come from the categories assessed from public evidence.
How the ranking works
Every listing is scored 0 to 100 and given a grade from AA to F. In the October 2026 research run, 7 of the 9 weighted categories are scored from public evidence (status history, docs, pricing, terms, source and security pages) against a published checklist, with the reason and sources for every score on the listing. Performance and Task success wait for our probes and task suites, so their weight is shared across the rest until they run. Negative events deduct up to 15 points. Read the methodology.
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