# Mailbox access APIs for AI agents

> 5 mailbox access ranked by the Anchor benchmark. Leader Nylas Email API (A). 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.

- Canonical: https://www.anchorterminal.com/categories/mailbox-access
- Markdown: https://www.anchorterminal.com/categories/mailbox-access.md (~2,050 tokens)
- Slim: https://www.anchorterminal.com/categories/mailbox-access.min.md (~380 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/categories/mailbox-access.json (this page as data, same URL with Accept: application/json)
- Site index for agents: https://www.anchorterminal.com/llms.txt (full text: https://www.anchorterminal.com/llms-full.txt)
- API: https://www.anchorterminal.com/api/v1/index.json
- Updated: 2026-10-08

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.

- Tools ranked: 5 · agent-ready (BB or better): 3 · accept x402: 0 · hosted endpoints: 4 · desk reviews by the panel: 0
- JSON: https://www.anchorterminal.com/api/v1/tools.json (list) · https://www.anchorterminal.com/api/v1/rankings.json (ranked) · https://www.anchorterminal.com/api/v1/x402.json (payable) · https://www.anchorterminal.com/api/v1/capabilities.json (by capability)
- Grades run AA, A, BB, B, C, D, E, F · methodology: https://www.anchorterminal.com/benchmark/

- Capabilities in this category: mailbox.read, mailbox.search, mailbox.send, mailbox.drafts, mailbox.sync
- https://letme.dev/mailbox.read picks the top-graded tool in this list and says how to call it direct; calling through letme comes later (https://www.anchorterminal.com/letme/index.md)

## Ranking

| # | Tool | Vendor | Kind | Category | Grade | Score | Confidence | x402 | Auth | Where | Reviews | Page |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 12 | Nylas Email API | Nylas | HTTP API | Mailboxes | A | 78.7 | medium | no | OAuth or key | hosted | none | https://www.anchorterminal.com/tools/nylas-email.md |
| 17 | Gmail API | Google | HTTP API | Mailboxes | BB | 77.8 | medium | no | OAuth | hosted | none | https://www.anchorterminal.com/tools/gmail-api.md |
| 106 | EmailEngine | Postal Systems OÜ | HTTP API | Mailboxes | BB | 71.4 | medium | no | API key | local | none | https://www.anchorterminal.com/tools/emailengine.md |
| 221 | Outlook Mail (Microsoft Graph) | Microsoft | HTTP API | Mailboxes | B | 66.3 | medium | no | OAuth | hosted | none | https://www.anchorterminal.com/tools/outlook-mail-graph.md |
| 402 | Unipile | UNIPILE SAS | HTTP API | Mailboxes | C | 58.4 | medium | no | API key | hosted | none | https://www.anchorterminal.com/tools/unipile.md |

Scores are from public evidence against the published checklist (https://www.anchorterminal.com/benchmark/), with Performance and Task success pending. p95 latency and context cost come from our probes, which haven't run yet.

## Summaries

### 12. Nylas Email API, A (78.7)

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. One REST schema covers Gmail, Microsoft 365, Exchange, Yahoo, iCloud and IMAP, and IAM API keys launched on 6 October 2026 can be bound to a single mailbox with chosen permissions. The status page lists eight email incidents between 24 July and 17 September 2026, most on IMAP sync and webhooks.

- Page: https://www.anchorterminal.com/tools/nylas-email · Markdown: https://www.anchorterminal.com/tools/nylas-email.md · JSON: https://www.anchorterminal.com/api/v1/tools/nylas-email.json
- Capabilities: mailbox.read, mailbox.search, mailbox.send, mailbox.drafts, mailbox.sync, email.threads · endpoint: `https://api.us.nylas.com/v3`

### 17. Gmail API, BB (77.8)

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. Fourteen OAuth scopes separate labels, sending, metadata and read-only access, and the quota page gives every method a unit cost. Eight of the scopes are restricted, read-only and metadata among them, so a public app that reads mail needs Google's verification and an annual third-party security assessment. Gmail mailboxes only.

- Page: https://www.anchorterminal.com/tools/gmail-api · Markdown: https://www.anchorterminal.com/tools/gmail-api.md · JSON: https://www.anchorterminal.com/api/v1/tools/gmail-api.json
- Capabilities: mailbox.read, mailbox.search, mailbox.send, mailbox.drafts, mailbox.sync · endpoint: `https://gmail.googleapis.com/gmail/v1`

### 106. EmailEngine, BB (71.4)

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. A self-hosted REST API over Gmail, Microsoft 365 and IMAP, with a public OpenAPI 3.0 spec and tokens that can be bound to one account, limited by action and group, and rate limited. It needs a server, Redis and a $1,450 yearly licence after a 14-day trial, and the MCP endpoint is a beta, off by default.

- Page: https://www.anchorterminal.com/tools/emailengine · Markdown: https://www.anchorterminal.com/tools/emailengine.md · JSON: https://www.anchorterminal.com/api/v1/tools/emailengine.json
- Capabilities: mailbox.read, mailbox.search, mailbox.send, mailbox.drafts, mailbox.sync

### 221. Outlook Mail (Microsoft Graph), B (66.3)

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. Delegated permissions split reading without bodies (Mail.ReadBasic), full reading, writing and sending, and delta queries and change notifications keep a local copy in step. sendMail takes no idempotency key and returns 202 before delivery, and each app is held to four concurrent requests per mailbox.

- Page: https://www.anchorterminal.com/tools/outlook-mail-graph · Markdown: https://www.anchorterminal.com/tools/outlook-mail-graph.md · JSON: https://www.anchorterminal.com/api/v1/tools/outlook-mail-graph.json
- Capabilities: mailbox.read, mailbox.search, mailbox.send, mailbox.drafts, mailbox.sync · endpoint: `https://graph.microsoft.com/v1.0`

### 402. Unipile, C (58.4)

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. One REST API covers Gmail, Outlook and IMAP with search, drafts, send with an idempotency key and new-mail webhooks, and the OpenAPI spec is public. The v1 access token reaches every connected account, scoped keys exist only in the v2 beta, and the status page shows three platform incidents between 21 July and 20 August 2026.

- Page: https://www.anchorterminal.com/tools/unipile · Markdown: https://www.anchorterminal.com/tools/unipile.md · JSON: https://www.anchorterminal.com/api/v1/tools/unipile.json
- Capabilities: mailbox.read, mailbox.search, mailbox.send, mailbox.drafts, mailbox.sync, calendar.read, calendar.write, calendar.webhooks, messaging.whatsapp, messaging.inbound · endpoint: `https://developer.unipile.com/mcp?branch=v1.0`

## 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.