Email for AI Agents
Give your AI agent its own email address. Send, receive, search, reply, and forward — right from Claude, Gemini, Codex, or any MCP-compatible client.
One command. No server to run. No SMTP to configure. Completely free.
Not a wrapper around SES or SendGrid. We built the entire email stack from the ground up — from receiving mail to delivering it to the inbox.
Why InboxAPI
Everything your AI agent needs to communicate over email.
Instant Setup
Your agent gets an @inboxapi.ai email address in seconds. No DNS configuration, no domain verification, no API keys to manage.
MCP Native
Works out of the box with Claude, Gemini, Codex, OpenCode, and any MCP-compatible client. Your agent can read, send, reply, forward, and search email like a human would.
Completely Free
No credit card. No usage tiers. No catch. We believe email should be a basic capability for every AI agent, not a line item. Paid plans with additional features are coming soon.
Full Email, Not Just Sending
Most services only let you send. InboxAPI gives your agent a real inbox — receive mail, search by sender or subject, follow conversation threads, check delivery status.
Built-In Abuse Prevention
Proof-of-work on signup, recipient caps, send quotas, and rate limiting. Every layer is designed to keep abuse off the platform.
Not a Wrapper
We don't sit on top of Amazon SES, Postfix, or SendGrid. We built and operate the entire email infrastructure ourselves.
How it works
Install
Connect to your AI client
Works with Claude Code, Claude Desktop, Gemini CLI, OpenCode, Codex, and more.
Start using email
Your agent automatically gets a unique email address (like bright-fuzzy-owl@inboxapi.ai). No signup forms, no config files.
What your agent can do
- Read and search its inbox
- Send emails to anyone
- Reply to and forward messages
- Follow conversation threads
- Check delivery status of sent mail
What you can build with it
Dev Team Coordination
Agents that email each other to coordinate a development workflow — one handles code review notifications, another tracks build failures, a third reports deployment status.
Monitoring & Alerts
Your agent watches a system, and when something breaks, it emails your team with context — not just a generic alert, but a diagnosis.
Newsletter Digest
An agent that receives newsletters and mailing lists, reads them, and sends you a daily summary of what actually matters.
Invoice & Receipt Processing
An agent that receives invoices by email, extracts line items and amounts, and feeds them into your accounting system.
Built for trust
Account Isolation
Each agent gets its own scoped account. Agents can only access their own data.
Email Authentication
SPF, DKIM, and DMARC are configured automatically for every message.
Abuse Prevention
Proof-of-work on signup, weekly recipient caps, send quotas, and rate limiting are all enforced by default.
Audit Trail
Token-based authentication ties every action to a specific account, so you always know what happened and when.
Credential Safety
Outbound emails containing authentication tokens are automatically rejected to help prevent accidental credential leaks.
Frequently asked questions
How is this different from AWS SES, SendGrid, or Resend?
Those are sending APIs — you build email infrastructure on top of them. InboxAPI gives your agent a complete email identity: send, receive, search, reply, and forward. There's nothing to configure and no infrastructure to manage.
How is this different from AgentMail or a1base?
We built our own email stack from the ground up. We don't wrap SES, Postfix, or any third-party sending service. Your agent's mail goes through infrastructure we operate directly.
Is it really free?
Yes. No credit card, no trial period, no usage tiers. We're working on paid plans with additional features, but the core experience will always be free.
How do you prevent spam and abuse?
Account creation requires proof-of-work. Each account can only email 5 unique external domains per week. Daily send quotas and rate limiting are enforced on every account. These constraints are structural — they're not policies, they're how the system works.
What about prompt injection via email?
Every inbound email includes a trust classification — trusted, agent, unverified, or suspicious — based on whether the sender is in your addressbook and whether their email passes authentication checks. This helps your agent decide how cautiously to handle each message. Emails from other InboxAPI agents are flagged separately so your agent knows to check with you before acting on them.
What about data exfiltration?
Outbound emails are scanned for authentication tokens and credentials. If your agent accidentally tries to send an email containing a JWT or access token, the message is rejected before it leaves the platform. This prevents agents from being tricked into leaking sensitive data via email.
Can agents spam each other?
The same send limits apply to all outbound email — recipient caps, quotas, and rate limiting work the same regardless of who's on the receiving end.
Will my agent's emails land in spam?
Maybe at first. Each agent gets a brand-new subdomain, and new senders don't have reputation yet. Recipients may need to check their spam folder for the first few emails. Over time, as your agent sends legitimate mail and recipients interact with it, delivery improves. Read more about email delivery.
Why email instead of a native agent protocol like A2A?
Email reaches the entire existing internet — billions of people and businesses already use it. A2A requires both sides to implement the protocol. When your agent needs to reach someone outside its own ecosystem, email is the universal option. Agents will likely need both.
Give your agent an email address
One command. Free forever.