The best email API for AI agents: what to look for
An agent needs to sign up, read a code and reply, without a human glancing at a mail client. These are the seven things to check in an email API for agents, and how the options measure up.
By Arin Prajapati, founder, 3 min read
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What an agent needs
An agent is not a person with a mail client. It cannot glance at an inbox, and it should not hold a key that opens everything. When you compare email APIs for agents, check these seven things:
- Its own inbox. An address the agent owns, created in one call, not a borrowed human mailbox.
- A blocking wait. One call that returns when the email arrives, so the agent does not poll in a loop and burn tokens.
- Extracted codes and links. The one time code or confirm link handed over as a field, not buried in HTML.
- A tool interface. Remote MCP, or a small stable HTTP API with errors that say what to fix.
- Scoped keys. A key that reaches one inbox and nothing else, revocable at once.
- Your own domain. Agent mail from
agent@yourcompany.comis trusted more than from a shared domain. - Cheap addresses. A fresh address per task, without paying per inbox.
We wrote up why each matters in giving AI agents an email address.
The options
AgentMail made inboxes for agents a category. It offers an API, Python and Node SDKs, MCP, IMAP and SMTP, and multi tenant pods, and it has a SOC 2 report on a higher plan. If you want official SDKs or enterprise options today, it is a strong choice. Our side by side lists the differences with sources.
Runearc covers the same ground and adds your own domain on the free plan, addresses that cost nothing through a catch-all, a single wait call that returns codes and links, and the same account sending your app email and running support@. It is newer, has no SDK yet, and access is limited.
Nylas reads and sends from your users' existing Gmail or Outlook accounts. That is a different job: pick it when the mailbox already exists and belongs to someone else.
Amazon SES or a sending API with your own inbound handling works if you want full control and are happy to build storage, threading, extraction and a wait endpoint. It is the cheapest and the most work.
Runearc is currently free. The paid Runearc prices below are planned and come from our pricing page; billing is not live yet.
Side by side
Swipe sideways to see the AgentMail column.
| Feature | Runearc | AgentMail |
|---|---|---|
| Agent-owned inboxes | ||
| Blocking wait with codes and links | Yes: one call | No dedicated endpoint documented |
| Remote MCP server | ||
| SDKs | REST, CLI and MCP; SDK coming | Python and Node |
| Inbox-scoped keys | ||
| Custom domain on the free plan | Yes, up to 3 | No: from the $20 plan |
| Also sends app email and runs support@ | Not stated | |
| SOC 2 and regions | Not yet | On higher plans |
Sources, read on November 9, 2026
- [1]AgentMail: www.agentmail.to
- [2]AgentMail pricing: www.agentmail.to/pricing
- [3]AgentMail MCP docs: docs.agentmail.to/integrations/mcp
- [4]Nylas: www.nylas.com
- [5]Amazon SES: aws.amazon.com/ses/
- [6]Model Context Protocol: modelcontextprotocol.io
Prices change. If something here is out of date or wrong, email hello@runearc.com and we will fix it.
How to pick
- Need SDKs or a compliance report now: AgentMail.
- Need the agent to use someone's existing mailbox: Nylas.
- Want full control and have time: Amazon SES plus your own inbound code.
- Want agent inboxes, your own domain and app email in one place, for free to start: Runearc. Connect it through MCP or follow the inbox walkthrough.
Not sure how it compares to the rest of the market? The best email API for developers guide covers all five jobs.
Questions
Can an AI agent use Gmail?
It can, through an API built on user mailboxes, but a personal Gmail account is built for a human: sign in prompts, consent screens and rate limits get in the way. For an agent that owns its address, a dedicated inbox from an agent email API is simpler and easier to limit.
What is the best email API for AI agents?
It depends on what the agent does. AgentMail and Runearc are built for agent-owned inboxes. Nylas is for reading existing user mailboxes. Sending-only APIs and Amazon SES work if you build inbound handling yourself. Check the seven needs on this page against your case.
Does the agent need MCP?
No. MCP lets a client such as Claude Code or Cursor use email as a tool without glue code. If you are writing the agent yourself, a plain HTTP API or SDK is just as good.
How do I stop an agent from emailing the wrong people?
Use a key scoped to one inbox, send from a sandboxed domain until you trust the agent, and treat incoming mail as untrusted input: check the SPF, DKIM and DMARC results before following a link.
Arin Prajapati, founder of RunearcA software engineer in Mumbai who builds Runearc's mail servers, API and site. More about Arin and why he built Runearc.
Read next
- Giving AI agents an email address: design notesAn agent is not a person with a mail client. It cannot glance at an inbox or click around. These are the decisions we made so an agent can use email in as few steps as possible.
- Runearc vs AgentMailBoth give agents their own inboxes over an API and MCP. AgentMail is further along; Runearc adds sending for apps, a support inbox and custom domains on the free plan.
- Give an MCP agent its own email addressMCP lets an agent use email the way it uses any other tool. Add one server to your client and the agent can create an inbox, send, reply and wait for a code.
Put Runearc to work
Get inboxes, sending, your own domains and MCP in one workspace. The free plan includes 3 inboxes, 3,000 emails a month and 3 custom domains, with no card.