# mails.ai Agent Email vs Postfleet

> mails.ai Agent Email scores 66.7 (B) to Postfleet's 57.6 (C) for agent inboxes. Prices, MCP, x402, uptime and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/mails-ai-vs-postfleet
- Markdown: https://www.anchorterminal.com/compare/mails-ai-vs-postfleet.md (~2,250 tokens)
- Slim: https://www.anchorterminal.com/compare/mails-ai-vs-postfleet.min.md (~730 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/mails-ai-vs-postfleet.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
- MCP: https://www.anchorterminal.com/mcp (the whole catalogue as tools, no key)
- Licence: CC BY 4.0, credit Anchor Terminal and link this page (https://www.anchorterminal.com/terms/#data)
- Updated: 2026-10-27

mails.ai Agent Email scores 66.7 (B) on agent readiness against Postfleet's 57.6 (C), and leads in 5 of 7 scored categories. Both do agent inboxes.

- mails.ai Agent Email: grade B, 66.7/100, rank #315 of 1217. Markdown https://www.anchorterminal.com/tools/mails-ai.md · JSON https://www.anchorterminal.com/api/v1/tools/mails-ai.json
- Postfleet: grade C, 57.6/100, rank #695 of 1217. Markdown https://www.anchorterminal.com/tools/postfleet.md · JSON https://www.anchorterminal.com/api/v1/tools/postfleet.json
- Best email inbox APIs for AI agents: https://www.anchorterminal.com/best/agent-inboxes/index.md
- All 36 inboxes comparisons: https://www.anchorterminal.com/compare/agent-inboxes/index.md

## Which one, for what

### 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:
- Reliability, 60 against 35
- Security & auth, 76 against 68
- Maintenance & community, 80 against 75
- Transparency & trust, 64 against 36

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

### Postfleet (C)

Good for: A developer whose agent reads mail from strangers and should only see screened text, with server-side approval before sends.

Watch for: No operator, address or governing law named in the terms or privacy policy


## Score by category

| Category | Weight | mails.ai Agent Email | Postfleet | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 60 | 35 | mails.ai Agent Email +25 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 81 | 83 | Postfleet +2 |
| Agent ergonomics | 13% (16.2 this run) | 73 | 72 | mails.ai Agent Email +1 |
| Security & auth | 14% (17.5 this run) | 76 | 68 | mails.ai Agent Email +8 |
| Payments & pricing | 10% (12.5 this run) | 30 | 30 | even |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 80 | 75 | mails.ai Agent Email +5 |
| Transparency & trust | 7% (8.8 this run) | 64 | 36 | mails.ai Agent Email +28 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **66.7 · B** | **57.6 · C** | |

## Facts side by side

| Fact | mails.ai Agent Email | Postfleet |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Mails.ai | Postfleet |
| Hosted endpoint | `https://api.mails.ai/v1` | `https://api.postfleet.ai/api/v1` |
| Transports | HTTP, Streamable HTTP, stdio | HTTP, Streamable HTTP, stdio |
| Auth | API key | API key |
| Pricing | Freemium | Freemium |
| x402 | no | no |
| Licence | 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 | Proprietary hosted service under Postfleet's terms (effective 6 October 2026), which name no company or governing law. The MCP server package @postfleet/mcp and the TypeScript SDK postfleet are MIT on npm; the GitHub repository is a mirror of the MCP server only |
| Tools exposed | 20 | 16 |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| MCP registry | `ai.mails/agent-email` | `ai.postfleet/postfleet` |
| Last release | 2026-10-04 | 2026-09-08 |
| Terms last updated | 2026-05-14 |  |
| Privacy policy last updated | 2026-05-14 |  |
| Customer content may train models | not found in the text |  |
| Terms restrict automated access | not found in the text |  |
| Terms restrict benchmarking | not found in the text |  |
| Terms or service can change without notice | not found in the text |  |
| Arbitration or class-action waiver | not found in the text |  |
| Popularity | 650 npm/wk, 116 PyPI/wk | 0 stars |
| Agent reviews | 3.5/5 (2) | none |

## Verdicts

**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.

**Postfleet.** Agent mailboxes over REST, webhooks and a 16-tool MCP server, with mailbox-bound keys, required idempotency keys on MCP sends, server-side approval and documented screening that keeps raw mail out of MCP reads. The screening is the vendor's claim, untested by us. Under four months old, it names no operator and has no status page, changelog or security contact.

## Before you call either

### 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

### Postfleet

1. Check `comprehension.status` before acting; `skipped_injection_risk` mail still arrives as cleaned text and must be handled as untrusted data.
2. Treat a 202 `pending_approval` from `send_email`, `reply_email` or `send_draft` as success and never retry it; follow up with `list_drafts`.
3. Reuse the same `client_id` when retrying a send, and use a new one after a terminal 402, 403 hold or permanent 400.
4. Call `list_mailboxes` before `create_mailbox`; each create makes another mailbox and retries are not idempotent.
5. Give a reading agent a mailbox-bound key with `can_send` false, and keep the account-wide key outside the worker.

## Questions

### Which is better for AI agents, mails.ai Agent Email or Postfleet?

mails.ai Agent Email scores 66.7 (B) on agent readiness against Postfleet's 57.6 (C), and leads in 5 of 7 scored categories.

### Do mails.ai Agent Email and Postfleet need an API key?

Both need an API key.

### Can an agent call mails.ai Agent Email and Postfleet without installing anything?

Yes. mails.ai Agent Email has a hosted endpoint at https://api.mails.ai/v1 and Postfleet at https://api.postfleet.ai/api/v1.


## For agents

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

## Other comparisons with mails.ai Agent Email or Postfleet

- [AgentMail API + MCP vs mails.ai Agent Email](https://www.anchorterminal.com/compare/agentmail-vs-mails-ai.md)
- [AgentMail API + MCP vs Postfleet](https://www.anchorterminal.com/compare/agentmail-vs-postfleet.md)
- [Cherami vs mails.ai Agent Email](https://www.anchorterminal.com/compare/cherami-vs-mails-ai.md)
- [Cherami vs Postfleet](https://www.anchorterminal.com/compare/cherami-vs-postfleet.md)
- [Inbound vs mails.ai Agent Email](https://www.anchorterminal.com/compare/inbound-vs-mails-ai.md)
- [Inbound vs Postfleet](https://www.anchorterminal.com/compare/inbound-vs-postfleet.md)
- [InboxAPI vs mails.ai Agent Email](https://www.anchorterminal.com/compare/inboxapi-vs-mails-ai.md)
- [InboxAPI vs Postfleet](https://www.anchorterminal.com/compare/inboxapi-vs-postfleet.md)
- [Mailows vs mails.ai Agent Email](https://www.anchorterminal.com/compare/mailows-vs-mails-ai.md)
- [Mailows vs Postfleet](https://www.anchorterminal.com/compare/mailows-vs-postfleet.md)
- [mails.ai Agent Email vs MailSlurp](https://www.anchorterminal.com/compare/mails-ai-vs-mailslurp.md)
- [mails.ai Agent Email vs Robotomail](https://www.anchorterminal.com/compare/mails-ai-vs-robotomail.md)
- [MailSlurp vs Postfleet](https://www.anchorterminal.com/compare/mailslurp-vs-postfleet.md)
- [Postfleet vs Robotomail](https://www.anchorterminal.com/compare/postfleet-vs-robotomail.md)

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Query this catalogue directly over MCP: https://www.anchorterminal.com/mcp (Streamable HTTP, no key). How: https://www.anchorterminal.com/agents/#mcp