Agent Mail Gateway

What Agent Mail Gateway does

Agent Mail Gateway keeps the mailbox password to itself. Each agent gets one API key for exactly one mailbox, and per-mailbox allow lists (name@domain or *@domain) decide whom the agent can receive mail from and write to. Mail from other senders is invisible to the agent and moved to Trash, or kept. Forged senders are rejected using the SPF, DKIM and DMARC results from your mail server. Incoming HTML is converted to Markdown to save tokens.

Outgoing mail is reviewed before it leaves. Built-in rules catch empty mails, attachment-only mails, 'see attached' without an attachment, leftover placeholders and duplicates. An optional LLM review, for example a local model in Ollama, and plain-language policies can be added. The gateway also manages calendar invitations, enforces an hourly send limit, keeps an audit log and sends signed webhooks on new mail that are compatible with Hermes Agent webhook routes. It offers MCP over Streamable HTTP, a stdio bridge and a REST API with OpenAPI docs at /docs.

Key features

• One API key per agent, mapped to exactly one mailbox
• Sender and recipient allow lists per mailbox
• Pre-send review with built-in rules, optional LLM check and custom policies
• HTML to Markdown conversion for reading, Markdown to HTML for sending
• Calendar invitations: send, update, cancel and respond
• Signed webhooks on new mail, compatible with Hermes Agent webhook routes

When to use it

• Giving a Hermes agent its own mailbox without sharing the IMAP/SMTP password
• Limiting an agent to replying only to approved contacts
• Letting an agent handle meeting invitations in Outlook, Gmail or Apple Calendar
• Reducing token cost of reading HTML-heavy email

Who it is for: Self-hosters who want AI agents to read and send email through an existing mail server with enforced limits.

How it fits with Hermes Agent

It supports Hermes Agent among other MCP and REST clients, with a Hermes Agent plugin and skill that teaches the agent to use its mailbox, plus webhook compatibility.

Requirements: An IMAP/SMTP mailbox on an existing mail server, and Docker to run the single container

FAQ