MX Lookup
Find the mail servers responsible for receiving email for any domain.
What is an MX record?
An MX (mail exchanger) record tells other mail servers where to deliver email for a domain. Each record pairs a hostname with a priority number.
MX records point at hostnames, never at IP addresses. The receiving hostname must itself resolve to an A or AAAA record.
Understanding MX priority
Lower numbers are tried first. A domain with priority 10 and priority 20 servers will have mail delivered to the 10 first, falling back to the 20 only when the first is unreachable.
Several records may share a priority. Sending servers distribute between equal-priority hosts, which is how providers spread inbound mail across multiple servers.
Common MX problems
No MX records at all means the domain is not set up to receive mail. Some senders will fall back to the domain’s A record, but this behaviour is not something to rely on.
An MX record pointing at a name with no address record will cause delivery failures, as will an MX record that points at an IP address instead of a hostname.
Publishing MX records does not by itself authorise anything to send mail as your domain. That is what SPF and DMARC do.