A mail server is a computer or service that handles email for a domain. It accepts incoming mail over SMTP, sends outgoing mail, stores messages in mailboxes and offers access through IMAP, POP3 or webmail.
Why it matters
The domain's MX records tell the world which mail server accepts its mail, so a mistake there stops all incoming messages. Running your own server gives control but also makes you responsible for security patches, spam filtering, TLS and IP reputation; most organisations instead use hosted services such as Google Workspace or Microsoft 365. A functioning setup also needs SPF, DKIM and DMARC records so that other servers trust its mail.
Example
For example.com the DNS might say:
example.com. 3600 IN MX 10 mail.example.com.
mail.example.com. 3600 IN A 203.0.113.25Senders look up the MX, connect to 203.0.113.25 on port 25 and deliver. If that host is down, senders queue and retry for days before bouncing.
Common mistakes
- Pointing an MX record at a CNAME or an IP address instead of a hostname with an A record.
- Self-hosting without reverse DNS (PTR) that matches the sending hostname.
- Having only one mail server with no backup plan and no monitoring.
Related
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