# Best email inbox APIs for AI agents (slim)

> AgentMail API + MCP (BB), Robotomail (B) and MailSlurp (B) lead the 7 ranked email inbox APIs. Picks by need, strengths, weaknesses and prices from the Anchor benchmark.

- Full: https://www.anchorterminal.com/best/agent-inboxes/index.md (~4,450 tokens) · this version ~1,180 tokens · JSON https://www.anchorterminal.com/best/agent-inboxes/index.json · canonical https://www.anchorterminal.com/best/agent-inboxes/
- Index: https://www.anchorterminal.com/llms.txt · API: https://www.anchorterminal.com/api/v1/index.json · Updated: 2026-10-09

All 7 ranked email inbox 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: 7 · agent-ready (BB or better): 1 · accept x402: 1 · hosted endpoints: 7
- Full ranked table: https://www.anchorterminal.com/categories/agent-inboxes.md
- Head-to-head comparisons: https://www.anchorterminal.com/compare/agent-inboxes/index.md (21)
- Methodology: https://www.anchorterminal.com/benchmark/index.md

## The shortlist

| # | Tool | Grade | Score | Best for | Price | Where |
| --- | --- | --- | --- | --- | --- | --- |
| 1 | [AgentMail API + MCP](https://www.anchorterminal.com/tools/agentmail.md) | BB | 74.9 | Agents that need their own address and carry email threads over days, including support, scheduling and outreach agents. | $2 / call | hosted and local |
| 2 | [Robotomail](https://www.anchorterminal.com/tools/robotomail.md) | B | 69.8 | A developer who wants one mailbox per agent with replies as events, on a small fixed monthly price. | $19 / mo | hosted |
| 3 | [MailSlurp](https://www.anchorterminal.com/tools/mailslurp.md) | B | 68.4 | QA and test agents that read OTP, verification and reset mail, and for supervised support agents where a person approves drafts. | $19.99 / mo | hosted |
| 4 | [mails.ai Agent Email](https://www.anchorterminal.com/tools/mails-ai.md) | B | 66.7 | Agents that send transactional mail and read replies, such as support, notification and verification agents, where an injection score on inbound mail is wanted out of the box. | $20 / mo | hosted and local |
| 5 | [Inbound](https://www.anchorterminal.com/tools/inbound.md) | B | 63.7 | A team that wants agent addresses on its own domain at a low fixed price, with IMAP and SMTP beside the API and an MCP mode that confines an agent to one mailbox. | $9 / mo | hosted |
| 6 | [Cherami](https://www.anchorterminal.com/tools/cherami.md) | C | 57.6 | A single developer or small team giving an agent a free, separate address for low-volume recurring correspondence such as supplier replies, project updates and agent-to-agent handoffs. | Free | hosted |
| 7 | [InboxAPI](https://www.anchorterminal.com/tools/inboxapi.md) | C | 54.5 | A personal mailbox for one coding agent that needs to exchange mail with its owner and a few contacts at no cost. | Free | hosted and local |

## Picks by need

- Highest score overall: [AgentMail API + MCP](https://www.anchorterminal.com/tools/agentmail.md), BB, 74.9/100 on the benchmark. Also [Robotomail](https://www.anchorterminal.com/tools/robotomail.md), B, 69.8/100.
- Reliability: [Inbound](https://www.anchorterminal.com/tools/inbound.md), 83/100 on reliability, against 61 for the overall leader.
- Schema & documentation: [Robotomail](https://www.anchorterminal.com/tools/robotomail.md), 90/100 on schema & documentation, against 85 for the overall leader.
- Security & auth: [mails.ai Agent Email](https://www.anchorterminal.com/tools/mails-ai.md), 76/100 on security & auth, against 62 for the overall leader.
- Transparency & trust: [Robotomail](https://www.anchorterminal.com/tools/robotomail.md), 73/100 on transparency & trust, against 68 for the overall leader.
- Paying per call with no account (x402): [AgentMail API + MCP](https://www.anchorterminal.com/tools/agentmail.md), accepts x402, $2 a call.

## How to choose

- How replies reach the agent: Check whether replies arrive by webhook, websocket or polling, since polling adds delay and cost to every check, and a webhook needs a public endpoint.
- Inbox creation and isolation: Check how an inbox is created and whether each can be isolated from others, since an agent that spawns many inboxes must keep their mail apart.
- Thread retention and matching: Check how long threads are retained and whether replies are matched to their original conversation, since an agent resuming after days needs its earlier messages still stored.
- Prompt injection screening: Check whether inbound messages are scanned for prompt injection before the agent reads them, since an email body is untrusted text that can carry instructions aimed at the agent.

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