Where they overlap
Both send from custom domains with DKIM and both can sign webhooks. Both expose a spam signal on inbound mail.
Where Innmail is different
Each agent has a persistent inbox with threads, labels, drafts, files and a calendar, reachable over REST, an MCP server and SDKs. Events are stored for 30 days and can be replayed. Policies hold risky sends for a person; inbound security checks for spoofing and prompt injection. SendGrid has no MCP server, no stored inbound and no agent concept.
When SendGrid fits better
Marketing campaigns, very high transactional volume and template-heavy sending are SendGrid's territory. Innmail's beta limits are sized for agents that converse, not for broadcasts.
Innmail and SendGrid at a glance
| Innmail | SendGrid | |
|---|---|---|
| Inbox per agent | One API call creates a real inbox per agent | No per-agent inboxes |
| Receiving and threads | Receives, stores and threads replies; read them over the API | Inbound Parse posts to your URL; nothing is stored or retrievable |
| 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 | Spam score in the parse payload |
| Events | Signed webhooks with retries, an SSE stream and a 30-day event log | Signed Event and Parse webhooks, opt-in |
| MCP and SDKs | MCP server, OpenAPI 3.1, SDKs for TypeScript, Python and Go, and a CLI | No first-party MCP server |
| 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 | No free plan; a 60-day trial |
Based on each product's public description as of 2026. Check SendGrid's site for current details.
Frequently asked questions
Can my agent send bulk email with Innmail?
No. Agent inboxes are for one-to-one and small-group conversation; the beta caps outside recipients per workspace per day and the terms prohibit unsolicited bulk mail.
Is there a free plan?
Innmail is free during the private beta. SendGrid retired its free plan in 2025 and offers a trial.
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