Running your own mail server is one of the hardest things to self-host, and one of the most tempting. It is not impossible, but delivery is the problem: big providers distrust small servers, and a single mistake can land your mail in spam. Know what you are getting into before you start.
Why it is hard
- Reputation. Major providers judge senders by IP address history. A new server starts with no reputation.
- Authentication. Without correct SPF, DKIM and DMARC records, mail is rejected or spammed.
- Reverse DNS. The IP must resolve back to your mail host name.
- Ongoing care. You patch, monitor queues and handle abuse reports.
Do
- Set SPF, DKIM and DMARC. They tell receivers that your server may send for your domain.
- Match the reverse DNS to your mail host name, and make sure the host name resolves to the same IP.
- Use TLS for sending and receiving.
- Start slowly. Send low volume at first, and only to people who expect your mail.
- Close open relay. Your server must only send for authenticated users.
- Back up the mailboxes and the configuration. See backups with restic or borg.
Do not
- Do not send bulk or marketing mail from a new server. Use a proper sending service for that.
- Do not leave ports 25, 143 or 110 open without authentication and TLS.
- Do not run mail on the same small server as everything else if you can avoid it.
- Do not ignore bounces and abuse reports.
Records you need
example.com. TXT "v=spf1 mx -all"
mail._domainkey TXT "v=DKIM1; k=rsa; p=PUBLIC_KEY"
_dmarc.example.com. TXT "v=DMARC1; p=quarantine; rua=mailto:postmaster@example.com"
example.com. MX 10 mail.example.com.Replace the values with your own. Test them with a mail tester before you rely on the setup.
Tools that help
Packaged mail servers such as Mailcow, Mail-in-a-Box and Stalwart handle the hard parts of setup. Compare them and read the current documentation. They still need a clean IP and the DNS records above.
Easier option: email with your hosting
If you mainly want a mailbox on your own domain, our free email hosting and web hosting plans include email with unlimited mailboxes, without running a server. That avoids the delivery problems above.