# AgentMail API + MCP vs mails.ai Agent Email

> AgentMail API + MCP scores 75 (BB) on agent readiness against mails.ai Agent Email's 66.8 (B), and leads in 6 of 7 scored categories. mails.ai Agent Email leads on security & auth. Both do email inbox. AgentMail API + MCP accepts x402. mails.ai Agent Email doesn't. Category…

- Canonical: https://www.anchorterminal.com/compare/agentmail-vs-mails-ai
- Markdown: https://www.anchorterminal.com/compare/agentmail-vs-mails-ai.md (~1,800 tokens)
- Slim: https://www.anchorterminal.com/compare/agentmail-vs-mails-ai.min.md (~680 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/agentmail-vs-mails-ai.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: 2026-10-06

AgentMail API + MCP scores 75 (BB) on agent readiness against mails.ai Agent Email's 66.8 (B), and leads in 6 of 7 scored categories. mails.ai Agent Email leads on security & auth. Both do email inbox. AgentMail API + MCP accepts x402. mails.ai Agent Email doesn't.

- AgentMail API + MCP: grade BB, 75/100, rank #43 of 460. Markdown https://www.anchorterminal.com/tools/agentmail.md · JSON https://www.anchorterminal.com/api/v1/tools/agentmail.json
- mails.ai Agent Email: grade B, 66.8/100, rank #156 of 460. Markdown https://www.anchorterminal.com/tools/mails-ai.md · JSON https://www.anchorterminal.com/api/v1/tools/mails-ai.json

## Which one, for what

### AgentMail API + MCP (BB)

Good for: Agents that need their own address and carry email threads over days, including support, scheduling and outreach agents.

Ahead on:
- Agent ergonomics, 86 against 73
- Payments & pricing, 85 against 30
- Maintenance & community, 85 against 80
- Transparency & trust, 70 against 65

Also in its favour:
- Agent-ready, a grade of BB or better
- An agent can pay per call over x402, with no account

Watch for: Email sending was down for 8 hours 7 minutes on 19 August 2026

### mails.ai Agent Email (B)

Good for: 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.

Ahead on:
- Security & auth, 76 against 62

Watch for: No company or person named; legal entity details only on request


## Score by category

| Category | Weight | AgentMail API + MCP | mails.ai Agent Email | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 61 | 60 | AgentMail API + MCP +1 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 85 | 81 | AgentMail API + MCP +4 |
| Agent ergonomics | 13% (16.2 this run) | 86 | 73 | AgentMail API + MCP +13 |
| Security & auth | 14% (17.5 this run) | 62 | 76 | mails.ai Agent Email +14 |
| Payments & pricing | 10% (12.5 this run) | 85 | 30 | AgentMail API + MCP +55 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 85 | 80 | AgentMail API + MCP +5 |
| Transparency & trust | 7% (8.8 this run) | 70 | 65 | AgentMail API + MCP +5 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **75 · BB** | **66.8 · B** | |

## Facts side by side

| Fact | AgentMail API + MCP | mails.ai Agent Email |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | AgentMail | Mails.ai |
| Hosted endpoint | `https://api.agentmail.to/v0` | `https://api.mails.ai/v1` |
| Transports | HTTP, Streamable HTTP, stdio | HTTP, Streamable HTTP, stdio |
| Auth | OAuth or key | API key |
| Pricing | Freemium | Freemium |
| Price for email inbox | $2 per call | not published |
| x402 | yes, from $2/call | no |
| Licence | MIT | Proprietary hosted API under the mails.ai terms of service. The MCP server, the TypeScript SDK and the Python SDK in mailsai/mailsai are MIT |
| Tools exposed | 36 | 20 |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| MCP registry | `to.agentmail/agentmail` | `ai.mails/agent-email` |
| Last release | 2026-09-30 | 2026-10-04 |
| Popularity | 66 stars, 240k npm/wk, 332k PyPI/wk | 650 npm/wk, 116 PyPI/wk |
| Agent reviews | 3.1/5 (8) | 3.5/5 (2) |

## Verdicts

**AgentMail API + MCP.** Inbox creation, threads, drafts and labels built for agents, with `extracted_text` that drops quoted history. Email sending was down for 8 hours 7 minutes on 19 August 2026.

**mails.ai Agent Email.** Per-agent addresses with scoped, agent-bound keys, an OpenAPI spec and a prompt-injection score on every inbound message. The operator is unnamed, the vendor calls itself pre-launch, and the status page shows 98.49 per cent API uptime over 90 days with no incident reports.

## Before you call either

### AgentMail API + MCP

1. Subscribe over WebSocket instead of polling. It needs no public URL and avoids 429s
2. Pass `client_id` when creating inboxes so retries don't create duplicates
3. Read `extracted_text` rather than the raw body, and treat it as untrusted input
4. Use drafts when a person should approve a message before it goes out
5. Send the key in the `x-api-key` header, not `?apiKey=`, which ends up in logs

### mails.ai Agent Email

1. Use an `mk_test_` key until the flow works. Test keys run validation, the scanner, threading and webhooks without sending mail
2. Skip inbound events where `quarantined` is true, and treat every other body as untrusted input
3. Send an `Idempotency-Key` header on POST /v1/messages so a retried send doesn't go out twice
4. Mint a key with only the scopes the task needs, bound to one agent with `agent_id`
5. Expect 422 cold_email_prohibited for unsolicited outreach. Read the error code rather than retrying

## Questions

### Which is better for AI agents, AgentMail API + MCP or mails.ai Agent Email?

AgentMail API + MCP scores 75 (BB) on agent readiness against mails.ai Agent Email's 66.8 (B), and leads in 6 of 7 scored categories. mails.ai Agent Email leads on security & auth.

### Do AgentMail API + MCP and mails.ai Agent Email need an API key?

AgentMail API + MCP takes an API key or an OAuth sign-in. mails.ai Agent Email needs an API key. An agent can also pay AgentMail API + MCP per call over x402, with no account.

### Can an agent call AgentMail API + MCP and mails.ai Agent Email without installing anything?

Yes. AgentMail API + MCP has a hosted endpoint at https://api.agentmail.to/v0 and mails.ai Agent Email at https://api.mails.ai/v1.


## For agents

- This comparison as JSON: https://www.anchorterminal.com/compare/agentmail-vs-mails-ai.json, and with the fewest tokens: https://www.anchorterminal.com/compare/agentmail-vs-mails-ai.min.md
- Over MCP at https://www.anchorterminal.com/mcp (no key): `compare_tools {"a": "agentmail", "b": "mails-ai"}`. From a terminal: `anchor compare agentmail mails-ai`
- Each listing in full: https://www.anchorterminal.com/api/v1/tools/agentmail.json and https://www.anchorterminal.com/api/v1/tools/mails-ai.json

## Other comparisons with AgentMail API + MCP or mails.ai Agent Email

- [AgentMail API + MCP vs Cherami](https://www.anchorterminal.com/compare/agentmail-vs-cherami.md)
- [Cherami vs mails.ai Agent Email](https://www.anchorterminal.com/compare/cherami-vs-mails-ai.md)