# Best mailbox access APIs for AI agents (slim)

> Nylas Email API (A), Gmail API (BB) and EmailEngine (BB) lead the 9 ranked mailbox access APIs. Picks by need, strengths, weaknesses and prices from the Anchor benchmark.

- Full: https://www.anchorterminal.com/best/mailbox-access/index.md (~5,900 tokens) · this version ~1,380 tokens · JSON https://www.anchorterminal.com/best/mailbox-access/index.json · canonical https://www.anchorterminal.com/best/mailbox-access/
- Index: https://www.anchorterminal.com/llms.txt · API: https://www.anchorterminal.com/api/v1/index.json · Updated: 2026-10-09

All 9 ranked mailbox access APIs on the Anchor benchmark, with a pick for each need and where each one falls short. Scores come from public evidence, re-checked as vendors change.

- Ranked: 9 · agent-ready (BB or better): 3 · accept x402: 0 · hosted endpoints: 5
- Full ranked table: https://www.anchorterminal.com/categories/mailbox-access.md
- Head-to-head comparisons: https://www.anchorterminal.com/compare/mailbox-access/index.md (36)
- Methodology: https://www.anchorterminal.com/benchmark/index.md

## The shortlist

| # | Tool | Grade | Score | Best for | Price | Where |
| --- | --- | --- | --- | --- | --- | --- |
| 1 | [Nylas Email API](https://www.anchorterminal.com/tools/nylas-email.md) | A | 78.7 | Products that act in their users' own mailboxes across several providers and want one schema, webhooks and OAuth handled. | $15 / mo | hosted |
| 2 | [Gmail API](https://www.anchorterminal.com/tools/gmail-api.md) | BB | 77.8 | An agent working in a Gmail or Google Workspace user's own mailbox, with search, threads, drafts, labels and incremental sync at no per-account fee. | Free | hosted |
| 3 | [EmailEngine](https://www.anchorterminal.com/tools/emailengine.md) | BB | 71.4 | A team that must keep mailbox access on its own infrastructure, has many mailboxes across Gmail, Microsoft 365 and IMAP, and can run a server and Redis. | $120.83 / mo | local |
| 4 | [Outlook Mail (Microsoft Graph)](https://www.anchorterminal.com/tools/outlook-mail-graph.md) | B | 66.3 | Agents working in Microsoft 365 or Outlook.com mailboxes that need scoped reading, drafting, sending and incremental sync. | Your plan | hosted |
| 5 | [Himalaya](https://www.anchorterminal.com/tools/himalaya.md) | B | 64.5 | An agent with a shell that must work in one person's existing mailbox on any provider, including plain IMAP hosts, without a hosted intermediary. | Free · OSS | local |
| 6 | [Unipile](https://www.anchorterminal.com/tools/unipile.md) | C | 58.4 | A product that needs one API over Gmail, Outlook and IMAP together with LinkedIn or WhatsApp messaging, priced per account. | $55 / mo | hosted |
| 7 | [Fastmail API (JMAP)](https://www.anchorterminal.com/tools/fastmail.md) | C | 54.1 | An agent working in its owner's own Fastmail mailbox, where JMAP gives batched reads, structured search and state-based sync on an open standard, and MCP gives a ready connection with read, write and send levels. | $6 / mo | local |
| 8 | [Zoho Mail API](https://www.anchorterminal.com/tools/zoho-mail.md) | D | 53.8 | An agent working inside its owner's Zoho Mail mailbox or administering a Zoho Mail organisation, where narrow scopes and the MCP server keep access small. | $1 / seat-mo | local |
| 9 | [Aurinko Email API](https://www.anchorterminal.com/tools/aurinko-email.md) | E | 44.2 | A product that connects many users' Gmail and Microsoft mailboxes and wants one schema, delta sync, tracking and webhooks at a low price per account. | Paid | hosted |

## Picks by need

- Highest score overall: [Nylas Email API](https://www.anchorterminal.com/tools/nylas-email.md), A, 78.7/100 on the benchmark. Also [Gmail API](https://www.anchorterminal.com/tools/gmail-api.md), BB, 77.8/100.
- Reliability: [Gmail API](https://www.anchorterminal.com/tools/gmail-api.md), 90/100 on reliability, against 77 for the overall leader.
- Agent ergonomics: [Gmail API](https://www.anchorterminal.com/tools/gmail-api.md), 82/100 on agent ergonomics, against 81 for the overall leader.
- Transparency & trust: [Gmail API](https://www.anchorterminal.com/tools/gmail-api.md), 82/100 on transparency & trust, against 81 for the overall leader.
- Self-hosting under an open licence: [EmailEngine](https://www.anchorterminal.com/tools/emailengine.md), self-hosted, Source available under the EmailEngine licence agreement licence.

## How to choose

- Scopes for read, draft and send: Check whether reading, drafting and sending need separate scopes, since an agent that only drafts replies should not be able to send mail on the person's behalf.
- Search filters and thread reads: Check how search filters by sender, date and label, and whether a whole thread returns in one call, since one-by-one reads use up limits.
- Sync delay and new-mail events: Check how long new mail takes to appear and whether an event is pushed on arrival, since polling for new mail uses up limit calls.
- Send limits and sending address: Check the send limit and the address mail is sent from, since a cap reached mid-task can leave a reply unsent.

- How the benchmark tests 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.

Each listing's verdict, strengths and weaknesses: https://www.anchorterminal.com/best/mailbox-access/index.md