Mailbay vs OpenMail
OpenMail and Mailbay both start from the same idea: an agent should have its own inbox. They differ on custom domains, policy controls and what else sits in the product.
Updated 3 min read
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In short
OpenMail is a focused, careful product for agent inboxes, with strong policy controls: allow and block rules at every level, and MCP scopes that let you withhold sending. Mailbay is broader: custom domains on the free plan, a blocking wait that extracts codes, sending for apps, and a support inbox for people.
Pick OpenMail if
- Fine grained allow and block rules for inbound and outbound mail matter most to you.
- You want an MCP server with OAuth and scopes that can leave out sending.
- You prefer billing in euros, with a spending limit on by default.
Pick Mailbay if
- You want a custom domain without paying.
- Your agent should block until an email arrives and get the code back in the same call.
- You also need app email from noreply@ and a shared support@ inbox.
Who each is for
OpenMail builds inboxes for AI agents, with signup automation (OTP codes, verification, 2FA) as a listed use case [1]. It bills in euros: a free plan with 3 inboxes and 3,000 emails a month, and Pro at €9 a month with usage based extras [2]. Custom domains need Pro [3].
Mailbay is for agents and the products around them. A workspace has projects, each with domains, inboxes, senders, keys and members, so the agent's inbox and the app's outgoing mail live side by side.
Features and prices
Mailbay is in private beta and free while it runs. The Mailbay prices below are the planned plans from our pricing page; billing is not live yet.
| Feature | Mailbay | OpenMail |
|---|---|---|
| Free plan | 3 inboxes, 3,000 emails a month, 3 custom domains | 3 inboxes, 3,000 emails a month, 3 GB, no custom domains [2] [3] |
| First paid plan | Pro, $9 a month: 25 inboxes, 50,000 emails, 10 domains | Pro, €9 a month: 10 inboxes, 10,000 emails, 10 GB, unlimited domains [2] [3] |
| Extra usage | $1 an inbox, $0.80 per 1,000 emails (planned) | €1 an inbox, €0.001 an email, €0.10 a GB [2] |
| Send limits | 100 recipients a day for a new account's first 7 days, then the plan's monthly volume | 10 a minute and 200 a day per inbox [4] |
| Wait for an email, codes extracted | Yes: wait in the API, CLI and MCP | No extraction or wait endpoint documented |
| Scoped API keys | Full, sending only, or one inbox; per project | Account, pod or inbox [5] |
| Allow and block lists | No | Yes, by address, domain or wildcard, at every scope [1] |
| MCP server | Remote (API key) and stdio | Remote with OAuth and scopes [6] |
| IMAP for mail apps | Yes | Not stated |
| Sending for apps from any verified address | Yes: POST /v1/emails and SMTP | Sends from inboxes |
| Shared support inbox for people | Yes | Not stated |
Sources, read on October 14, 2026
- [1]OpenMail home page: openmail.sh
- [2]OpenMail FAQ (plans and prices): docs.openmail.sh/pages/resources/faq
- [3]OpenMail, custom domains: docs.openmail.sh/concepts/custom-domains
- [4]OpenMail, rate limits: docs.openmail.sh/concepts/rate-limits
- [5]OpenMail, API key scopes: docs.openmail.sh/best-practices/api-key-scopes
- [6]OpenMail, MCP: docs.openmail.sh/integrations/mcp
Prices change. If something here is out of date or wrong, email hello@mailbay.dev and we will fix it.
Where OpenMail is better
- Policy controls. OpenMail's allow and block rules work on inbound and outbound mail at account, pod and inbox level, and fail closed. Mailbay has no allowlists yet. If an agent must only ever talk to a fixed set of domains, this is a real advantage.
- MCP auth. OAuth with scopes, so a client can read without being able to send. Mailbay's remote MCP server takes an API key today; OAuth is planned. You can get part of the way with an inbox scoped key.
- Unlimited domains on Pro, where Mailbay's planned Pro has 10.
Where Mailbay is better
- Custom domains on the free plan, with one click DNS on Vercel and Cloudflare and a wizard that keeps existing Google Workspace or iCloud mail working.
- Codes without parsing.
wait_for_emailreturnscodesandlinksnext to the message. See email inboxes for AI agents. - More included volume. 50,000 emails and 25 inboxes on the planned Pro plan.
- App email and people. Send from noreply@ over the API or SMTP, and run support@ in a shared inbox or Apple Mail.
Moving from OpenMail
- Create a project per pod, or one project with an inbox key per agent.
- Recreate inboxes with
POST /v1/inboxes, or use the Catch-all and pass the address towaitwith itstofilter. - Point your MCP client at Mailbay with an API key (see MCP docs).
- Move custom domains: delete them in OpenMail, add them in Mailbay, publish the new MX, SPF and DKIM records. Mail already received stays in OpenMail.
Read next
- Mailbay vs AgentMailBoth give agents their own inboxes over an API and MCP. AgentMail is further along; Mailbay adds sending for apps, a support inbox and custom domains on the free plan.
- Give an MCP agent its own email addressMCP lets an agent use email the way it uses any other tool. Add one server to your client and the agent can create an inbox, send, reply and wait for a code.
- An email inbox for your AI agentAn agent that signs up for things needs an address that receives mail, and a way to get the code out of it without polling. Here is the whole flow in three steps.
Join the beta
Mailbay is in private beta and free while the beta runs: inboxes, sending, your own domains and MCP. We invite people in small batches and read every note on the form.