Sendmux

Sendmux is an email API for teams building AI agents that need a real inbox. It lets you create agent-specific mailboxes, send outbound through your own providers, and receive inbound messages as clean, structured events.

It’s a good fit if you’re tired of gluing together separate sending and inbox tools, or if your agents need reliable, provider-flexible email handling with less parsing overhead.

• Agent mailboxes Create inboxes per agent (on @myagent.mx or your custom domain) so each agent has a dedicated place to receive messages.
• Structured inbound (not raw HTML) Get extracted message content as structured JSON, with signatures and quoted history stripped by default, and optional fields like links, headers, and attachment metadata.
• Outbound sending via HTTP or SMTP Send from a mailbox using the mailbox credential, with idempotency-key support for safe HTTP retries.
• Provider flexibility (BYO + built-in sending) Send through connected providers or use the built-in account if you don’t want to configure one yet.
• Routing controls Distribute traffic using quotas (second, minute, hour, day) and weighted delivery across eligible providers or delivery groups.
• Automatic failover If a provider goes down, Sendmux reroutes before the failure reaches your users.
• Receive without polling Use signed webhooks and SSE (server-sent events) for live mailbox clients.