Where they overlap
Both send over an API, support custom domains with DKIM, sign webhooks, publish an MCP server and SDKs, and have a free tier with a daily cap. Resend can receive mail at a domain and fetch bodies over its API.
Where Innmail is different
Innmail's unit is the agent inbox: one persistent address with threads, labels, drafts, a file drive and a calendar. Policies hold risky sends for a person, inbound mail is checked for spoofing and prompt injection, and every action is in an audit log. Resend's inboxes are in a private beta and its receiving is domain-wide without a thread object.
When Resend fits better
If you are sending application email (receipts, password resets, notifications) at volume from a product, Resend's sending-first design, templates and analytics are the better fit. Innmail is for agents that need to converse.
Innmail and Resend at a glance
| Innmail | Resend | |
|---|---|---|
| Inbox per agent | One API call creates a real inbox per agent | Inboxes are in private beta; the product is built around sending domains |
| Receiving and threads | Receives, stores and threads replies; read them over the API | Receives at a domain; bodies are fetched over the API, no thread object |
| Human approval | Policies hold risky outbound mail for a person to approve; no key can approve | No |
| Inbound security | Checks for spoofing, lookalike domains, pressure language and prompt injection; can hold mail before the agent reads it | No inbound security checks documented |
| Events | Signed webhooks with retries, an SSE stream and a 30-day event log | Svix-signed webhooks |
| MCP and SDKs | MCP server, OpenAPI 3.1, SDKs for TypeScript, Python and Go, and a CLI | Official MCP server and SDKs |
| Custom domains | Your own domain with DKIM, verified from the UI; unlimited inboxes on it | Yes |
| Free tier | Free beta: 3 @innmail.app inboxes and 100 outside recipients a day per workspace | Free: 3,000 emails a month, 100 a day; paid from $20 a month |
Based on each product's public description as of 2026. Check Resend's site for current details.
Frequently asked questions
Can I use both?
Yes. Many teams send product email with Resend and give their agents Innmail inboxes; nothing in Innmail depends on your transactional provider.
Does Innmail have an MCP server like Resend?
Yes, hosted at /api/v1/mcp, covering inboxes, threads, messages, drafts, events, calendar and verification codes, without an approve tool.
What does it cost?
Nothing during the private beta: 3 @innmail.app inboxes and 100 outside recipients a day per workspace, unlimited inboxes on a domain you verify. Mail between your own agents is not counted.
Give every AI agent its own inbox.
A real @innmail.app address in one API call, or one on your own domain. Free in the private beta, no Gmail to connect.
Request beta access