What an MX record does
An MX (mail exchanger) record tells other mail servers where to deliver email for a domain. Each record has a priority and a host name. Senders try the lowest number first and fall back to higher numbers if it is unavailable.
Common problems this reveals
- No MX registros – mail may be delivered to the domain’s A record instead, or bounce entirely.
- An MX pointing at a CNAME – not allowed by the RFCs, and some senders will reject it.
- An MX pointing at an IP address – the target must be a host name that has its own A or AAAA record.
- Old provider still listed – after moving to Google Workspace or Microsoft 365, stale MX records cause lost mail.
