3.1.3. MX records

MXrecords - records that indicate the addresses of mail servers that accept incoming mail sent to domain mailboxes.

MX record priorities work according to the order in which the specified servers are available. That is, only if a server with a lower priority is unavailable, records with a higher priority will be used. For example, when specifying mx20.example.com with priority 20 and mx10.example.com with priority 10, only recording for mx10.example.com, since it has a lower priority, and only if the server specified in this entry is unavailable, connections will be directed to mx20.example.com.

Due to the principle of how priorities work, it is not recommended to specify different MXs from different services for the same domain.