Is it possible to have multiple MX records for one domain?
Yes, it's possible to have more than one MX record for one domain.
Moreover, it is possible to assign priorities to them.
- Log into Plesk.
- Go to Plesk > Domains > example.com > DNS Settings;
- From the drop-down menu next to Specify the priority of the mail exchange server choose a value;
- Press OK.
The MX priority determines the order in which servers are supposed to be contacted (if several servers with different priorities are given): the server(s) with the highest priority (and the lowest preference number) will be tried first.