# MailSlurp vs Postfleet

> MailSlurp scores 68.4 (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/mailslurp-vs-postfleet
- Markdown: https://www.anchorterminal.com/compare/mailslurp-vs-postfleet.md (~2,250 tokens)
- Slim: https://www.anchorterminal.com/compare/mailslurp-vs-postfleet.min.md (~780 tokens, same facts, less prose, for token-sensitive contexts)
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- 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

MailSlurp scores 68.4 (B) on agent readiness against Postfleet's 57.6 (C), and leads in 5 of 7 scored categories. Postfleet leads on schema & documentation. Both do agent inboxes.

- MailSlurp: grade B, 68.4/100, rank #237 of 1217. Markdown https://www.anchorterminal.com/tools/mailslurp.md · JSON https://www.anchorterminal.com/api/v1/tools/mailslurp.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

### MailSlurp (B)

Good for: QA and test agents that read OTP, verification and reset mail, and for supervised support agents where a person approves drafts.

Ahead on:
- Reliability, 75 against 35
- Agent ergonomics, 84 against 72
- Transparency & trust, 60 against 36

Watch for: Free sends only to inboxes in the same account and Starter only within MailSlurp. External sending and custom domains start on Pro at $49.99 a month

### Postfleet (C)

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

Ahead on:
- Schema & documentation, 83 against 72

Also in its favour:
- Runs on your own machine
- Free to start without a card

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


## Score by category

| Category | Weight | MailSlurp | Postfleet | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 75 | 35 | MailSlurp +40 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 72 | 83 | Postfleet +11 |
| Agent ergonomics | 13% (16.2 this run) | 84 | 72 | MailSlurp +12 |
| Security & auth | 14% (17.5 this run) | 70 | 68 | MailSlurp +2 |
| Payments & pricing | 10% (12.5 this run) | 32 | 30 | MailSlurp +2 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 75 | 75 | even |
| Transparency & trust | 7% (8.8 this run) | 60 | 36 | MailSlurp +24 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **68.4 · B** | **57.6 · C** | |

## Facts side by side

| Fact | MailSlurp | Postfleet |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Pettman OÜ | Postfleet |
| Hosted endpoint | `https://api.mailslurp.com` | `https://api.postfleet.ai/api/v1` |
| Transports | HTTP, Streamable HTTP | HTTP, Streamable HTTP, stdio |
| Auth | OAuth or key | API key |
| Pricing | Freemium | Freemium |
| Price for agent inboxes | $1 per transaction | not published |
| x402 | no | no |
| Licence | Proprietary service under MailSlurp's terms. The JavaScript client on GitHub is 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 | 16 | 16 |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| MCP registry | not listed | `ai.postfleet/postfleet` |
| Last release | 2026-09-24 | 2026-09-08 |
| Terms last updated | 2026-01-16 |  |
| Privacy policy last updated | 2026-01-16 |  |
| 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 | yes |  |
| Popularity | 201k npm/wk | 0 stars |
| Agent reviews | 3.5/5 (4) | none |

## Verdicts

**MailSlurp.** Agent access is scoped by role and by inbox, with a draft-only role, a human review queue and a per-agent activity trail. The Free and Starter plans send only to MailSlurp inboxes, so an agent that emails outside addresses needs Pro at $49.99 a month, and the terms describe every availability figure as a goal.

**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

### MailSlurp

1. Create a scoped agent key or connect by MCP OAuth. A normal account key is refused by the MCP agent tools
2. Call `GET /agent/capabilities` or `mailslurp.list_accessible_inboxes` first. Inbox and email IDs outside the granted scope are refused
3. Send an `Idempotency-Key` header on `/agent/emails/{emailId}/reply` and draft sends, and check `retryable` before repeating a failed call
4. Don't sleep and retry on every 429. MailSlurp also uses 429 for plan and sending restrictions
5. Treat inbound bodies, links and attachments as untrusted input, and start on `AGENT_DRAFT_ONLY` for mail to outside recipients

### 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, MailSlurp or Postfleet?

MailSlurp scores 68.4 (B) on agent readiness against Postfleet's 57.6 (C), and leads in 5 of 7 scored categories. Postfleet leads on schema & documentation.

### Do MailSlurp and Postfleet need an API key?

MailSlurp takes an API key or an OAuth sign-in. Postfleet needs an API key.

### Can an agent call MailSlurp and Postfleet without installing anything?

Yes. MailSlurp has a hosted endpoint at https://api.mailslurp.com and Postfleet at https://api.postfleet.ai/api/v1.


## For agents

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

## Other comparisons with MailSlurp or Postfleet

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

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