Postal is the only free, MIT-licensed package here that actually delivers mail rather than handing it to somebody else. That makes it genuinely powerful and genuinely demanding — it publishes a real minimum spec, and it wants MariaDB, not MySQL.
4 GB RAM
2 CPU cores · 25 GB disk · MariaDB 10.6+
Postal is a complete, MIT-licensed mail server you host yourself. It delivers outbound mail directly from your own IP address, accepts inbound mail, tracks what happened to each message, and exposes an HTTP API — the job a paid service like Mailgun or SendGrid does, without the per-message bill. It runs as a Docker Compose stack and needs MariaDB 10.6 or newer specifically; the project states that MySQL is not supported in its place. Its documented minimum is 2 CPU cores, 4 GB RAM and 25 GB of disk, which means the cheapest VPS plans genuinely will not do.
Related: All six packages compared · Postal vs PowerMTA · SMTP VPS · Port 25 · rDNS
Understanding which box it fills saves a lot of wasted setup.
Mailgun, SendGrid, Amazon SES, Postmark — Postal does the same job on your own hardware. Same direct delivery, same API, same message tracking, same webhooks. What changes is that the sending reputation, the queue and the maintenance all become yours, and the per-message fee disappears.
Taken from the project's own documentation on 17 August 2026, not from a hosting page's estimate. The source is named underneath so you can check it.
| Licence | MIT |
|---|---|
| Cost | Free |
| Stack | Docker and Docker Compose |
| Database | MariaDB 10.6 or higher — the project states plainly that MySQL is not supported in its place |
| Also needs | Needs git, curl and jq, and outbound Port 25. Requires database credentials able to create and drop databases. |
| Sends mail itself | Yes — it is a mail transfer agent |
Sources, checked 17 August 2026
Read at each vendor's own documentation rather than taken from a summary. Follow the links and check for yourself — figures like these move.
It is excellent software and it is not for everybody. Better to find out now.
Per-message pricing scales badly. At a certain volume a fixed monthly server cost is simply cheaper, and Postal has no licence fee on top.
Postal gives you HTTP send endpoints, webhooks and per-message tracking. If you are integrating mail into an application, that is the interesting part.
The supported install is Docker Compose. If that sentence is unremarkable to you, the setup will be straightforward.
Few self-hosted options handle both directions well. Postal does, which makes it a real choice for application mail that has to receive replies.
Its published minimum is 2 cores and 4 GB. Trying to squeeze it onto 1 GB will waste your afternoon and then your money.
At low volume a relay's free or cheap tier costs less than your time. Self-hosting pays off with volume, not with principle.
Running an MTA means owning bounces, complaint loops and blocklists. If no one will look at those, a relay is doing you a favour.
MariaDB 10.6+ is required and MySQL is not accepted in its place. That is a hard constraint, not a preference.
Postal publishes a real minimum — 2 CPU cores, 4 GB RAM and 25 GB of disk — so this is arithmetic rather than an upsell. The smallest plan that clears it is below; the cheaper plans are genuinely too small and we would rather not sell you one.
Matches the documented minimum almost exactly — 2 cores and 4 GB — with NVMe for MariaDB and the queue.
2 Cores · 2 GB RAM
30 GB NVMe · 10 Gbps Port
$12.95/mo
This is a starting point, not a rule — list size and sending frequency matter more than the software itself. See all plans · compare all six packages · ask before you order.
Port 25 open from the first second, a dedicated IPv4 address and reverse DNS set free on request — plus a 7-day money-back guarantee if Postal turns out not to suit you.
