Postmark is the real thing — its own MTAs, no SES underneath, a deservedly great deliverability record. mailstein takes that same owned-infrastructure philosophy and hands it to you: your server, your IP, your logs, transactional and broadcast on one meter, billed per send.
Full credit where it's due: Postmark runs its own infrastructure, is obsessive about transactional deliverability, and has some of the best support in the business. If you want that reliability fully managed and never want to touch a server, they earned their reputation honestly. This page is for teams who want to own the box instead of renting it.
Postmark and mailstein agree on the hard part — real MTAs, no shared SES pool. The difference is who the infrastructure answers to.
The places it counts when email is carrying real revenue.
| mailstein | Postmark | |
|---|---|---|
| Runs its own MTAs (no SES) | Yes | Yes |
| Who owns the sending server | You do | Postmark does |
| Who owns your IP & reputation | You do | Postmark's IPs |
| Message logs & retention | On your box, as long as you want | Hosted, 45-day retention |
| Transactional + broadcast, one platform | One meter, one price | Broadcast is a separate product |
| Billed per send, never per contact | Yes | Per email (premium) |
| Dedicated IP + managed warm-up | Included | Add-on / higher tiers |
| Automatic SPF · DKIM · DMARC | Yes | Yes |
| Clean SDK · CLI · MCP for agents | Yes | SDK, no MCP |
| REST API & SMTP | Yes | Yes |
| Free tier without a card | 50/mo, 1 domain | 100/mo trial |
Not abstractions — the moments where it actually bites.
Postmark's deliverability is excellent — but it's Postmark's IP and Postmark's reputation. On mailstein you warm and own the IP itself, so the sending history you invest in is an asset on your infrastructure, not theirs.
Postmark retains message activity for 45 days. mailstein keeps every message and event on your own box for as long as you choose — search a send from last quarter without hitting a retention wall.
Postmark sells broadcast as a separate product and prices email at a premium. mailstein runs transactional and broadcast on a single per-send meter — never per contact — so a growing list never inflates the invoice.
REST API, SMTP, templates, contacts, campaigns, domains, webhooks, suppressions, and analytics — plus an SDK, CLI, and an MCP server so an agent can send, look up a delivery, or manage a domain without a human in the loop.
The developer experience you expect from a modern transactional platform — a single call to send, typed SDKs, webhooks for every event. The difference is where it leaves from: a mailstein server that's yours, not a shared endpoint.
Everything Postmark gets right about owned MTAs and clean transactional delivery — running on a server that answers to you, at a per-send price with broadcast included. Verify a domain and send in five minutes.
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