Head to head · Agent inboxes · October 2026 research run
MailSlurp vs Robotomail
Robotomail scores 69.8 (B) on agent readiness against MailSlurp's 68.4 (B), and leads in 4 of 7 scored categories. MailSlurp leads on agent ergonomics and security & auth. Both do agent inboxes.
Best email inbox APIs for AI agents · All 21 inboxes comparisons
Which one, for what
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
- Agent ergonomics, 84 against 72
- Security & auth, 70 against 65
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
Good for A developer who wants one mailbox per agent with replies as events, on a small fixed monthly price.
Ahead on
- Schema & documentation, 90 against 72
- Transparency & trust, 73 against 60
Also in its favour
- Free to start without a card
Watch for
The Free plan allows 10 sends and 10 receives a month, only with the owner's verified address, and discards other inbound mail
Score by category
| Category | Weight this run | MailSlurp | Robotomail | Edge |
|---|---|---|---|---|
| Reliability | 16%20 | 75 | 73 | MailSlurp +2 |
| Performance | 10%pending | pending | pending | not scored in this run |
| Schema & documentation | 13%16.2 | 72 | 90 | Robotomail +18 |
| Agent ergonomics | 13%16.2 | 84 | 72 | MailSlurp +12 |
| Security & auth | 14%17.5 | 70 | 65 | MailSlurp +5 |
| Payments & pricing | 10%12.5 | 32 | 35 | Robotomail +3 |
| Task success | 10%pending | pending | pending | not scored in this run |
| Maintenance & community | 7%8.8 | 75 | 77 | Robotomail +2 |
| Transparency & trust | 7%8.8 | 60 | 73 | Robotomail +13 |
| Negative events | ≤15 | 0 | 0 | |
| Total | 68.4 · B | 69.8 · B |
Facts side by side
| Fact | MailSlurp | Robotomail |
|---|---|---|
| Kind | HTTP API | HTTP API |
| Vendor | Pettman OÜ | Tiny Bot Labs Limited |
| Hosted endpoint | https://api.mailslurp.com | https://api.robotomail.com/v1 |
| Transports | HTTP, Streamable HTTP | HTTP, Streamable HTTP |
| Auth | OAuth or key | OAuth or 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 service under Robotomail's terms of service. The five SDKs on GitHub are MIT |
| Tools exposed | 16 | 6 |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| Last release | 2026-09-24 | 2026-09-25 |
| Terms last updated | 2026-01-16 | 2026-10-05 |
| Privacy policy last updated | 2026-01-16 | 2026-09-01 |
| 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 | yes | not found in the text |
| Popularity | 201k npm/wk | 20 npm/wk |
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.
Robotomail
A public OpenAPI 3.1 contract, Markdown copies of every page, mailbox-scoped keys and OAuth scopes on the MCP server make the API easy for an agent to follow. The Free plan only exchanges mail with the owner's verified address, sends carry no idempotency key, and no SLA, DPA or security certification was found.
Before you call either
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
Robotomail
- After
POST /v1/signup, ask the owner to click the verification link. Product routes return 403 until then - On Free, send only to the owner's verified address. Mail from anyone else is discarded and can't be recovered by upgrading
- If a send times out, list
direction=OUTBOUNDmessages before retrying. There is no idempotency key - Reply with the RFC
messageIdininReplyTo, not the Robotomail UUID, to stay in the thread - Treat every inbound body and attachment as untrusted input, and deduplicate webhooks on
X-Robotomail-Delivery-Id
Questions
Which is better for AI agents, MailSlurp or Robotomail?
Robotomail scores 69.8 (B) on agent readiness against MailSlurp's 68.4 (B), and leads in 4 of 7 scored categories. MailSlurp leads on agent ergonomics and security & auth.
Do MailSlurp and Robotomail need an API key?
Both take an API key or an OAuth sign-in.
Can an agent call MailSlurp and Robotomail without installing anything?
Yes. MailSlurp has a hosted endpoint at https://api.mailslurp.com and Robotomail at https://api.robotomail.com/v1.
Other comparisons with MailSlurp or Robotomail
Machine-readable
- This page as Markdown
/compare/mailslurp-vs-robotomail.md· slim.min.md· JSON.json(or sendAccept: text/markdown) - Each listing in full
/api/v1/tools/mailslurp.json·/api/v1/tools/robotomail.json - From a terminal
anchor compare mailslurp robotomail(the CLI) - Over MCP
compare_tools {"a": "mailslurp", "b": "robotomail"}at/mcp, no key