Mailbay vs Postmark
Postmark has spent years earning a reputation for fast, reliable transactional email. Mailbay is newer, and puts inboxes, agents and sending in one product.
Updated 5 min read
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In short
Postmark is the transactional email service people recommend when delivery speed and inbox placement matter most, and it has the history to back that up. It even publishes live time to inbox numbers per mailbox provider [6]. Mailbay is newer and still warming its IPs. What it adds is the receiving side: inboxes for agents and people, next to sending.
Pick Postmark if
- Password resets and receipts must land fast and you want a long, public deliverability record.
- You want templates, separate transactional and broadcast streams, and long retention options.
- You send at volume today and want dedicated IPs.
Pick Mailbay if
- You need inboxes that receive, thread and reply, for agents or for support@.
- You want a generous free plan to build on: Postmark's free plan is 100 emails a month.
- You want one product for app email, agent inboxes and a shared support inbox.
Who each is for
Postmark is for product teams sending transactional email, with broadcast mail kept in a separate stream so it cannot hurt the transactional reputation [3]. Inbound processing turns received mail into JSON posted to your webhook [2].
Mailbay is for apps and agents that both send and receive. Received mail is stored in inboxes you can read, search, wait on and reply from, over the API, MCP, IMAP or the dashboard.
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 | Postmark |
|---|---|---|
| Free plan | 3,000 emails a month, 3 inboxes, 3 domains | 100 emails a month, no overages [1] |
| Entry paid plan | Pro, $9 a month for 50,000 emails | Basic, $15 a month for 10,000 emails, then $1.80 per 1,000 [1] |
| Other plans | Scale, $99 a month for 250,000 emails | Pro $16.50 and Platform $18 a month for 10,000 emails, then $1.30 and $1.20 per 1,000 [1] |
| Receiving | Inboxes with threads, a Catch-all, wait for a code, IMAP | Inbound webhooks, listed on Pro and Platform [1] [2] |
| Transactional and broadcast separation | Separate IP pools for free, paid and our own mail; no broadcast sending yet | Message streams [3] |
| SMTP | 587 (STARTTLS) and 465 (TLS) | 25, 2525 or 587 with STARTTLS [4] |
| Templates | No | Yes [1] |
| Dedicated IPs | Enterprise plan (planned) | From $50 a month per IP, 300,000+ emails a month on Pro or higher [1] |
| MCP server | Remote and stdio, with inbox and wait tools | Local server, run with npx [5] |
| Shared support inbox for people | Yes | Not stated |
| Published delivery speed | Not yet | Live time to inbox charts [6] |
Sources, read on October 14, 2026
- [1]Postmark pricing: postmarkapp.com/pricing
- [2]Postmark, inbound email: postmarkapp.com/inbound-email
- [3]Postmark, message streams: postmarkapp.com/message-streams
- [4]Postmark, send email with SMTP: postmarkapp.com/developer/user-guide/send-email-with-smtp
- [5]Postmark, MCP server: postmarkapp.com/lp/mcp/
- [6]Postmark, time to inbox: tti.postmarkapp.com
Prices change. If something here is out of date or wrong, email hello@mailbay.dev and we will fix it.
Where Postmark is better
- Deliverability track record. This is the big one. Inbox placement is earned over years of sending wanted mail from the same IPs and domains. Postmark has that history; our IPs are in warmup. If a delayed password reset costs you customers today, that matters more than anything else on this page.
- Transactional tooling. Templates, message streams, configurable retention and a mature dashboard for searching sent mail.
- Dedicated IPs at volume on a self serve plan.
Where Mailbay is better
- Receiving is first class. Mail lands in inboxes with threads and auth results instead of only being forwarded to a webhook. Agents can block on
waitand get codes back. - support@ for people. A shared inbox with assignment and keyboard shortcuts, forwarding, and IMAP app passwords for Apple Mail. See support@ on your own domain.
- The free plan is enough to build on. 3,000 emails a month and 3 custom domains.
- Agents. A remote MCP server whose tools create inboxes and wait for mail.
Why we chose to run our own servers, and what that costs us while the IPs warm up, is in Why we run our own mail servers.
Moving from Postmark
- Add your sending domain in Mailbay. Postmark's DKIM record uses its own selector, so both can stay published while you switch; add Mailbay's SPF include next to any existing one.
- Over SMTP: change the host to
smtp.mailbay.dev, port 587 or 465, usernamemailbayand a Mailbay sending key as the password. - Over the API: map Postmark's fields to
POST /v1/emails:Fromtofrom,Tototo,HtmlBodytohtml,TextBodytotext,ReplyTotoreply_to. Templates have to be rendered on your side first. - Inbound: instead of a webhook per message, create inboxes and subscribe to
message.received(see Webhooks), or read them over IMAP.
Postmark's own write ups on deliverability are worth reading whichever service you pick; start with their time to inbox page.
Read next
- 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.
- Why we run our own mail serversMost email APIs are a layer over someone else's sending service. We chose to run the mail path ourselves. Here is what that means, what it costs, and why we think it is worth it.
- support@ on your own domain, without Google WorkspaceMost small SaaS products need two or three shared addresses, not a seat per person. Here is how to run support@ on your domain, keep the mail you already have, and answer from a shared inbox or Apple Mail.
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.