What is Mails.ai?
Mails.ai is an email API for developers building AI agents that need their own addresses and conversations. Mails.ai supports sending, receiving, and replying to email while keeping threads and reputation information separate for each agent. The service exposes structured reply data rather than requiring developers to parse raw MIME, and provides a dashboard for monitoring messages, delivery metrics, and live events.
What Mails.ai can do
Mails.ai combines email delivery with inbound processing and controls for agent-driven workflows. Received messages carry prompt-injection scores and sender reputation information, while high-risk messages arrive with a quarantine flag. Mails.ai also supports extracting authentication details from email and separating message composition from delivery through drafts and scheduled sends.
- Mails.ai gives each agent an inbox with threaded messages and replies.
- Mails.ai delivers reply, delivery, and bounce events through signed webhooks or a live stream.
- Mails.ai extracts sign-in codes and magic links into separate fields.
- Mails.ai saves messages as drafts or schedules them for later delivery.
- Mails.ai exposes per-agent reputation scores through the API.
- Mails.ai checks outgoing messages against a suppression list.
How Mails.ai works
Mails.ai provides self-serve API keys, and each workspace starts with an agent named hello. Developers can send through Node.js or Python SDKs, plain HTTP, or MCP tools for coding agents. Reply listeners receive scanned events that include quarantine information. The supplied examples check that flag before passing a reply onward, allowing application code to exclude messages identified as high risk.
- Mails.ai supports integrations including Claude Code, Cursor, Windsurf, Cline, and Continue.
- Mails.ai provides test keys that run the API without sending real mail or billing.
- Mails.ai supplies [email protected] for testing a complete send-and-reply workflow.
Who Mails.ai is for
Mails.ai targets engineers and teams building agents that communicate by email. The page describes support agents with individual addresses, agents that prepare drafts for human review, and applications that wait for sign-in messages. Mails.ai also supports teams working across Python and Node.js, with SDK access and event handling for incorporating email into existing agent workflows.
- Mails.ai supports support-agent conversations with separate addresses and threads.
- Mails.ai supports human review of agent-written drafts before sending.
- Mails.ai supports automated retrieval of emailed authentication codes and magic links.
- Mails.ai supports tests that wait for an actual reply event.
Mails.ai pricing and plans
Mails.ai offers a free tier without requiring a credit card, alongside paid plans. Custom-domain sending is available on any paid plan and requires DKIM, SPF, and DMARC records at the domain registrar, without moving nameservers. Mails.ai offers a dedicated IP on request with Scale. Sending and receiving have separate allowances, according to the customer account quoted on the page.
Mails.ai strengths and limitations
Mails.ai combines agent-specific inboxes, structured events, and inbound scanning in the same service. Webhooks are HMAC-signed and retried with backoff, and delivery events include identifiers for handling duplicates. Shared sending infrastructure is already warm by default. These capabilities support agent email workflows, but access to custom domains and dedicated IPs depends on the selected plan, and complaint rates can trigger automatic sending restrictions.
- Mails.ai restricts custom-domain sending to paid plans.
- Mails.ai provides dedicated IP addresses on request with Scale.
- Mails.ai automatically pauses a sender when its complaint rate reaches 0.3%.
Mails.ai FAQ
What is Mails.ai?
Mails.ai is an email API that gives AI agents individual addresses for sending, receiving, and replying to messages. Mails.ai provides threaded inboxes, structured reply events, per-agent reputation scores, and inbound prompt-injection scanning for developers building email-enabled agents.
Is Mails.ai free?
Mails.ai offers a free tier with no credit card required. Mails.ai also has paid plans, with custom-domain sending available on any paid plan and dedicated IP addresses available on request with Scale.
Does Mails.ai support SDKs and MCP?
Mails.ai supports Node.js and Python SDKs, a REST API, and MCP access. Mails.ai lists integrations with coding and agent tools including Claude Code, Cursor, Windsurf, Cline, Continue, LangGraph, and Pydantic AI.
How does Mails.ai handle prompt injection in email?
Mails.ai scores inbound email for prompt injection on every plan and flags high-risk messages as quarantined. Mails.ai includes injection scores in reply events, and the example code skips quarantined replies before passing message content to an agent.
Can Mails.ai send email from a custom domain?
Mails.ai supports custom-domain sending on any paid plan. Mails.ai requires DKIM, SPF, and DMARC records at the registrar without a nameserver move, and sends custom-domain mail through mail servers the service runs itself.
Can developers test Mails.ai without sending real email?
Mails.ai provides a test key that runs the API without sending real mail or billing. Mails.ai also provides [email protected], a test address that answers within about a second and replies at most 3 times in a thread.
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