What is an MX record?
An MX (mail exchanger) record is a DNS record that names a server accepting email for a domain, with a priority number. Sending servers try the lowest number first and move to higher ones when it does not answer. A domain with no MX record has no declared place for its mail to go.
Reading the result
Hosts are listed lowest priority number first, which is the order senders try them. Hosts with equal numbers share the load. Under the list, the tool names the provider the hosts belong to, such as Google Workspace or Microsoft 365, when it recognises them.
Beat runs on the same engine, on a schedule, across all 41 checks and 25 blacklists. What it adds is asking again, noticing when an answer changes and telling you what to do about it.
Common MX record problems
No MX records
The domain cannot receive mail, so replies and bounces to it are lost. Some receivers also refuse mail from a sending domain that cannot receive any.
An MX pointing at a CNAME or an IP address
An MX target must be a hostname with its own address records. RFC 2181 forbids pointing an MX at an alias (a CNAME), and an IP address in that field is not valid either.
Hosts from two providers
Records left over from an old provider split incoming mail between two systems, and the messages that land on the old one are often never read.
A null MX
A single MX of "0 ." (RFC 7505) declares that the domain accepts no mail at all. That is right for a parked domain and wrong for one that sends.