Head to head · Email inbox · October 2026 research run
mails.ai Agent Email vs Robotomail
Robotomail scores 69.8 (B) on agent readiness against mails.ai Agent Email's 66.7 (B), and leads in 4 of 7 scored categories. mails.ai Agent Email leads on security & auth. Both do email inbox.
Which one, for what
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 65
Also in its favour
- Runs on your own machine
Watch for
No company or person named; legal entity details only on request
Good for A developer who wants one mailbox per agent with replies as events, on a small fixed monthly price.
Ahead on
- Reliability, 73 against 60
- Schema & documentation, 90 against 81
- Payments & pricing, 35 against 30
- Transparency & trust, 73 against 64
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 | mails.ai Agent Email | Robotomail | Edge |
|---|---|---|---|---|
| Reliability | 16%20 | 60 | 73 | Robotomail +13 |
| Performance | 10%pending | pending | pending | not scored in this run |
| Schema & documentation | 13%16.2 | 81 | 90 | Robotomail +9 |
| Agent ergonomics | 13%16.2 | 73 | 72 | mails.ai Agent Email +1 |
| Security & auth | 14%17.5 | 76 | 65 | mails.ai Agent Email +11 |
| Payments & pricing | 10%12.5 | 30 | 35 | Robotomail +5 |
| Task success | 10%pending | pending | pending | not scored in this run |
| Maintenance & community | 7%8.8 | 80 | 77 | mails.ai Agent Email +3 |
| Transparency & trust | 7%8.8 | 64 | 73 | Robotomail +9 |
| Negative events | ≤15 | 0 | 0 | |
| Total | 66.7 · B | 69.8 · B |
Facts side by side
| Fact | mails.ai Agent Email | Robotomail |
|---|---|---|
| Kind | HTTP API | HTTP API |
| Vendor | Mails.ai | Tiny Bot Labs Limited |
| Hosted endpoint | https://api.mails.ai/v1 | https://api.robotomail.com/v1 |
| Transports | HTTP, Streamable HTTP, stdio | HTTP, Streamable HTTP |
| Auth | API key | OAuth or 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 service under Robotomail's terms of service. The five SDKs on GitHub are MIT |
| Tools exposed | 20 | 6 |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| MCP registry | ai.mails/agent-email | not listed |
| Last release | 2026-10-04 | 2026-09-25 |
| Terms last updated | 2026-05-14 | 2026-10-05 |
| Privacy policy last updated | 2026-05-14 | 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 | not found in the text | not found in the text |
| Popularity | 650 npm/wk, 116 PyPI/wk | 20 npm/wk |
| 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.
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
mails.ai Agent Email
- Use an
mk_test_key until the flow works. Test keys run validation, the scanner, threading and webhooks without sending mail - Skip inbound events where
quarantinedis true, and treat every other body as untrusted input - Send an
Idempotency-Keyheader on POST /v1/messages so a retried send doesn't go out twice - Mint a key with only the scopes the task needs, bound to one agent with
agent_id - Expect 422 cold_email_prohibited for unsolicited outreach. Read the error code rather than retrying
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, mails.ai Agent Email or Robotomail?
Robotomail scores 69.8 (B) on agent readiness against mails.ai Agent Email's 66.7 (B), and leads in 4 of 7 scored categories. mails.ai Agent Email leads on security & auth.
Do mails.ai Agent Email and Robotomail need an API key?
mails.ai Agent Email needs an API key. Robotomail takes an API key or an OAuth sign-in.
Can an agent call mails.ai Agent Email and Robotomail without installing anything?
Yes. mails.ai Agent Email has a hosted endpoint at https://api.mails.ai/v1 and Robotomail at https://api.robotomail.com/v1.
Other comparisons with mails.ai Agent Email or Robotomail
Machine-readable
- This page as Markdown
/compare/mails-ai-vs-robotomail.md· slim.min.md· JSON.json(or sendAccept: text/markdown) - Each listing in full
/api/v1/tools/mails-ai.json·/api/v1/tools/robotomail.json - From a terminal
anchor compare mails-ai robotomail(the CLI) - Over MCP
compare_tools {"a": "mails-ai", "b": "robotomail"}at/mcp, no key