How Mailbay compares
Five products people weigh Mailbay against, with what each costs, what it does, and where it is the better choice. Every competitor fact links to its source.
Updated
The comparisons
- 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.4 min read
- Mailbay vs OpenMailOpenMail 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.3 min read
- Mailbay vs ResendResend is a polished, proven sending API. Mailbay accepts the same request body for sending, so moving is a base URL and a key, and it adds inboxes people and agents read.5 min read
- Mailbay vs PostmarkPostmark has spent years earning a reputation for fast, reliable transactional email. Mailbay is newer, and puts inboxes, agents and sending in one product.5 min read
- Mailbay vs MailosaurMailosaur is a testing tool: email and SMS, previews, spam checks and SDKs for every test framework. Mailbay covers the email part of that and also sends real mail.3 min read
At a glance
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.
| Product | Built for | Free plan, per month | First paid plan | Receives mail as |
|---|---|---|---|---|
| Mailbay | Agents, app email and support inboxes | 3,000 emails, 3 inboxes, 3 domains | $9 a month (planned) | Inboxes, Catch-all, IMAP |
| AgentMail | Inboxes for AI agents | 3,000 emails, 3 inboxes, no custom domain | $20 a month | Inboxes, IMAP |
| OpenMail | Inboxes for AI agents | 3,000 emails, 3 inboxes, no custom domain | €9 a month | Inboxes |
| Resend | Sending from apps, marketing | 3,000 emails, 100 a day, 3 domains | $20 a month | Inbound webhooks |
| Postmark | Transactional sending | 100 emails a month | $15 a month | Inbound webhooks |
| Mailosaur | Email and SMS testing | 14 day trial | $20 a month, billed annually | Test inboxes |
Read from each product's public pricing and docs on October 14, 2026. The sources are linked on each comparison page.
How we write these
We only state what a competitor publishes on its own site, and link the page we read with the date we read it. Where we could not find something, the table says “Not stated” rather than guessing. Each page has a section on where the other product is the better choice, because for some of you it will be. If we got something wrong, email hello@mailbay.dev and we will correct it.
Read next
- What people build with MailbaySix jobs Mailbay does well, each with a walkthrough you can copy. The requests and code on these pages were run against a real Mailbay stack before we published them.
- Giving AI agents an email address: design notesAn agent is not a person with a mail client. It cannot glance at an inbox or click around. These are the decisions we made so an agent can use email in as few steps as possible.
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.