MXrecords - records defining the addresses of mail servers that should accept incoming mail sent to mailboxes of the domain.
MX record priorities work according to the order in which the specified servers are available. That is, only if the server with a lower priority is unavailable, records with a higher priority will be used. For example, when specifying
mx20.example.com with priority
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
Due to the principle of work of priorities, it is not recommended to specify different MXs from different services for one domain.