Mailgun handles email delivery. MultiMail adds the agent identity layer, graduated oversight controls, and compliance tooling that AI agents require in production.
Mailgun is a well-engineered transactional email API built for human-authored messages. When an AI agent sends email through Mailgun, there is no mechanism to declare the sending identity as an AI system, no way to require human approval before high-stakes messages are delivered, and no built-in path to EU AI Act compliance. Developers building agent systems on Mailgun end up bolting on approval queues, audit logs, and disclosure headers manually — and those homegrown solutions rarely hold up under compliance review. The missing layer is not deliverability; it is agent-aware infrastructure.
MultiMail provides the same high-volume email delivery developers expect from Mailgun, with an additional layer designed specifically for AI agents: a cryptographically signed identity claim that proves which agent sent a message, graduated oversight modes that let you gate sends on human approval without rebuilding your webhook stack, pre-send domain intelligence to catch reputation problems before delivery, and EU AI Act disclosure compliance out of the box. Migrating from Mailgun is a single endpoint swap to `POST /v1/mailboxes/{mailbox_id}/send`. What you gain is the agent trust and compliance infrastructure that Mailgun does not provide.
Replace your Mailgun API calls with POST https://api.multimail.dev/v1/mailboxes/{mailbox_id}/send. The sender is the mailbox in the path plus your bearer key — there is no `from` field. Map your message into `to`, `subject`, and `markdown` (MultiMail converts markdown to formatted HTML on delivery).
You do not add an identity field — MultiMail signs every outbound message with an X-MultiMail-Identity claim: an ECDSA P-256 signed payload covering the oversight mode, capabilities, the AI-generated flag, and the operator plus mailbox identity. Recipients and compliance auditors can verify which agent sent the message without trusting the From address alone.
Set oversight_mode: gated_send on your mailbox to hold all outbound sends in a pending queue until a human approves them. Use list_pending to surface queued messages and decide_email to approve or reject. Reads and replies to inbound mail proceed autonomously.
Point your inbound MX or forwarding rules at MultiMail. Inbound messages fire a webhook to your endpoint with parsed headers, body, and attachments. Use check_inbox and read_email to pull messages programmatically from your agent loop.
MultiMail evaluates recipient domain reputation, DMARC alignment, and EU AI Act disclosure requirements before each send. Messages that would damage deliverability or violate disclosure rules are flagged before they leave the queue, not after a bounce.
Pick your platform, copy the prompt, and paste it to your AI agent — it sets up MultiMail and builds the whole flow. Nothing to fill in.
Every message sent through MultiMail carries an X-MultiMail-Identity header: an ECDSA P-256 signed claim over the oversight mode, capabilities, AI-generated flag, and operator plus mailbox identity. Unlike a custom From address, this claim is verifiable by recipients and auditors even after the message passes through forwarding rules or mailing list processors.
Mailgun delivers messages immediately. MultiMail's gated_send mode holds outbound sends in a queue that a human reviews via POST /v1/oversight/decide or the decide_email MCP tool — no approval webhook infrastructure to build and maintain. Switch modes per mailbox as your deployment matures.
EU AI Act Article 50 requires that AI-generated communications be disclosed to recipients. Every agent-originated message carries an X-AI-Generated: true header plus a human-readable disclosure footer. This is gateway-enforced per mailbox — the ai_disclosure setting is locked on and cannot be disabled. Mailgun has no equivalent.
Before a message leaves the queue, MultiMail checks recipient domain reputation, DMARC alignment, and known spam-trap patterns. Problems surface as warnings on the pending record before delivery, giving the oversight reviewer or the agent itself a chance to cancel rather than absorb a bounce.
Migration is a swap to POST /v1/mailboxes/{mailbox_id}/send. Mailgun's to and subject map directly; the sender becomes the mailbox in the path (no from field), and the body becomes a single markdown field that MultiMail renders to HTML on delivery. Identity is signed on automatically, so there is no agent_id to add.
Email infrastructure built for AI agents. Verifiable identity, graduated oversight, and a hosted MCP server. Formally verified in Lean 4.