Mails.ai
Verified Oct 16, 2026 ActiveEmail inboxes and delivery infrastructure for autonomous agents
Listed on EffectHub ·
Pricing
- Pricing model
- Freemium
- Paid options from
- $20/mo
- Billing
- Monthly
Free covers 3,000 events and one agent; Pro $20 and Scale $99 raise send and inbound volume plus agent count, with per-call metered pricing announced and a $50/month dedicated IP add-on.
Use tool ↗About Mails.ai
Mails.ai provisions real, addressable mailboxes for software agents: a single API call sends, receives and threads replies, and inbound mail is returned as structured events rather than raw MIME. Every incoming message passes a six-category prompt-injection scanner, and each sending agent carries a reputation score that pauses it automatically when the score falls. Cold outreach is refused at the API rather than merely prohibited in the terms, and an MCP server exposes the same operations to Claude and other agent clients.
- Platforms
- Web · API
- API
- Yes
- Last verified
- Oct 16, 2026
Verified sources
- Free 3,000 events / Pro $20 / Scale $99 per month, metered tier announced, $50 dedicated IP add-onmails.ai ↗
- Positioned as email infrastructure for AI agents; injection scanner, reputation scoring, MCP server, cold email blocked at the APImails.ai ↗
- Published SDK @mailsai/sdk, latest version 0.2.3registry.npmjs.org ↗
Is Mails.ai legit?
We don’t label tools safe or unsafe. Below are the records we checked ourselves, each with the date we read it.
- Domain registered
- Aug 2, 2022 (4 years ago)Registry record (RDAP), registrar NameCheap, Inc., looked up Sep 6, 2026
- TLS certificate
- Issued by Let's Encrypt, valid until Jan 7, 2027Seen in our own connection to the site on Oct 16, 2026
- Last checked
- Oct 16, 2026The site answered
Pros & cons of Mails.ai
Worth it if you are shipping agents that email real people and you do not want to build inbound parsing and injection defence yourself. The blanket cold-email refusal is a feature, not a limitation — it is what keeps the shared sending reputation usable.
Pros
- prompt-injection scoring on inbound mail is rare among email APIs
- TypeScript and Python SDKs published on npm plus an MCP server
- free tier is enough to prototype a single agent end to end
- per-agent reputation isolation with an optional dedicated IP
Cons
- young product — the public SDK is still on a 0.x release
- no company name, legal entity or location disclosed on the site
- metered pricing is still marked coming soon, so cost at scale is unsettled
- automatic reputation pausing can silence an agent mid-workflow
Best for
- agents that send confirmations and follow-ups and must handle human replies
- products where inbound email needs to arrive as structured events
- teams that want injection scoring applied to untrusted inbound mail
- MCP-based agent stacks needing an email tool without custom glue
Not for
- cold outbound or bulk marketing sequences, which the API rejects outright
- plain transactional email, where Postmark or Resend are cheaper and more mature
- anyone who needs a mailbox UI for human staff
Watch out: Note the pivot: most catalogue listings still describe Mails.ai as a cold-email outreach suite with unlimited inboxes, and that exact use case is now blocked at the API.