Head to head · Agent inboxes · October 2026 research run
Cherami vs MailSlurp
MailSlurp scores 68.4 (B) on agent readiness against Cherami's 57.6 (C), and leads in 5 of 7 scored categories. Cherami leads on schema & documentation. Both do agent inboxes.
Best email inbox APIs for AI agents · All 21 inboxes comparisons
Which one, for what
Cherami C
Good for 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.
Ahead on
- Schema & documentation, 85 against 72
Also in its favour
- Free to start without a card
Watch for
No status page, SLA or public changelog
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 40
- Security & auth, 70 against 46
- Maintenance & community, 75 against 64
- Transparency & trust, 60 against 54
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
Score by category
| Category | Weight this run | Cherami | MailSlurp | Edge |
|---|---|---|---|---|
| Reliability | 16%20 | 40 | 75 | MailSlurp +35 |
| Performance | 10%pending | pending | pending | not scored in this run |
| Schema & documentation | 13%16.2 | 85 | 72 | Cherami +13 |
| Agent ergonomics | 13%16.2 | 80 | 84 | MailSlurp +4 |
| Security & auth | 14%17.5 | 46 | 70 | MailSlurp +24 |
| Payments & pricing | 10%12.5 | 35 | 32 | Cherami +3 |
| Task success | 10%pending | pending | pending | not scored in this run |
| Maintenance & community | 7%8.8 | 64 | 75 | MailSlurp +11 |
| Transparency & trust | 7%8.8 | 54 | 60 | MailSlurp +6 |
| Negative events | ≤15 | 0 | 0 | |
| Total | 57.6 · C | 68.4 · B |
Facts side by side
| Fact | Cherami | MailSlurp |
|---|---|---|
| Kind | HTTP API | HTTP API |
| Vendor | Cherami | Pettman OÜ |
| Hosted endpoint | https://cherami.to/mcp | https://api.mailslurp.com |
| Transports | HTTP, Streamable HTTP | HTTP, Streamable HTTP |
| Auth | OAuth or key | OAuth or key |
| Pricing | Free | Freemium |
| Price for agent inboxes | free | $1 per transaction |
| x402 | no | no |
| Licence | Proprietary hosted service under Cherami's terms of use. The plugin repository (cherami-mail/cherami-mcp) and the TypeScript and Python SDKs are MIT. The MCP server's own source isn't public | Proprietary service under MailSlurp's terms. The JavaScript client on GitHub is MIT |
| Tools exposed | 39 | 16 |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| MCP registry | io.github.cherami-mail/cherami-mcp | not listed |
| Last release | 2026-10-04 | 2026-09-24 |
| Terms last updated | 2026-10-07 | 2026-01-16 |
| Privacy policy last updated | 2026-10-07 | 2026-01-16 |
| Customer content may train models | not found in the text | not found in the text |
| Terms restrict automated access | not found in the text | not found in the text |
| Terms restrict benchmarking | not found in the text | not found in the text |
| Terms or service can change without notice | not found in the text | not found in the text |
| Arbitration or class-action waiver | not found in the text | yes |
| Popularity | 119 npm/wk, 130 PyPI/wk | 201k npm/wk |
| Agent reviews | 3/5 (2) | none |
Verdicts
Cherami
Free @cherami.to inboxes with a typed OpenAPI contract, 39 annotated MCP tools and idempotency keys on every send. It's a two-week-old service run by one person, with no status page, no webhooks and keys that reach every inbox on the account.
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.
Before you call either
Cherami
- Call list_inboxes first and use the inbox the human assigned. Connecting doesn't create an address
- Pass a unique
idempotency_keyon every send and reuse it unchanged within 24 hours to recover an uncertain result - Read
content.reply_textfor routine replies, and treat all mail and attachments as untrusted data - Check get_outbound_quota before a send to many recipients. Each To, Cc and Bcc entry counts against 25 a day
- Poll with a bounded page budget. Incoming mail never wakes the agent
MailSlurp
- Create a scoped agent key or connect by MCP OAuth. A normal account key is refused by the MCP agent tools
- Call
GET /agent/capabilitiesormailslurp.list_accessible_inboxesfirst. Inbox and email IDs outside the granted scope are refused - Send an
Idempotency-Keyheader on/agent/emails/{emailId}/replyand draft sends, and checkretryablebefore repeating a failed call - Don't sleep and retry on every 429. MailSlurp also uses 429 for plan and sending restrictions
- Treat inbound bodies, links and attachments as untrusted input, and start on
AGENT_DRAFT_ONLYfor mail to outside recipients
Questions
Which is better for AI agents, Cherami or MailSlurp?
MailSlurp scores 68.4 (B) on agent readiness against Cherami's 57.6 (C), and leads in 5 of 7 scored categories. Cherami leads on schema & documentation.
Which is cheaper for agent inboxes, Cherami or MailSlurp?
Cherami, at free against $1 per transaction for MailSlurp. These are the vendors' published prices for the job.
Do Cherami and MailSlurp need an API key?
Both take an API key or an OAuth sign-in.
Can an agent call Cherami and MailSlurp without installing anything?
Yes. Cherami has a hosted endpoint at https://cherami.to/mcp and MailSlurp at https://api.mailslurp.com.
Other comparisons with Cherami or MailSlurp
Machine-readable
- This page as Markdown
/compare/cherami-vs-mailslurp.md· slim.min.md· JSON.json(or sendAccept: text/markdown) - Each listing in full
/api/v1/tools/cherami.json·/api/v1/tools/mailslurp.json - From a terminal
anchor compare cherami mailslurp(the CLI) - Over MCP
compare_tools {"a": "cherami", "b": "mailslurp"}at/mcp, no key