Self-hosting
Why nobody can run their own mail server anymore (almost)
In the late nineties it was a weekend project. Today one bad neighbour on a shared IP address can end it.
Installing a mail server is still easy. Getting the mail delivered is the hard part, and the problem is not your software. It is the address you send from.
The obstacles, in order of how often they bite
- Port 25 is closed. The major clouds block outbound SMTP by default to stop spam from their own customers. You have to ask for it to be opened, and they can say no.
- A new IP has no reputation. Providers treat unknown senders with suspicion, so a new server gets throttled or spammed for weeks while it "warms up".
- The address may already be listed. Cloud and VPS IP ranges are often used by spammers before you get them, so you inherit their listings.
- Reverse DNS must match. The name the server announces must match the reverse record of its IP, or many servers refuse it.
- Authentication is mandatory for bulk. SPF, DKIM and DMARC must all pass, and the rules for large senders are stricter every year.
- Home and dynamic ranges are blocked outright by public lists, so a home server is a non-starter.
What it costs
- The server itself: a few dollars a month.
- The time: months of warm-up, monitoring of blocklists, and handling abuse reports.
- The risk: one compromised account turns your address into a spam source, and every other message you send pays for it.
So what do people do?
- Send through a relay that already has reputation (a transactional email provider or an API router).
- Keep your own mailbox server only for personal mail, where volume is low and the risk is yours.
- Use the relay's domain, or your own domain with its authentication records, so the reputation attaches to you, not to a box.