How to change mail server's domain name?
Domain is delegated to the Plesk DNS:
- Navigate to Domains > example.com > DNS Settings;
- Click on MX record;
Mail exchange serverto the desired domain.
Domain is not delegated to the Plesk DNS:
Find authoritative DNS provider for the domain:
# dig +short example.com NS
Navigate to the DNS provider's web-interface and login;
Set MX record to the desired domain.
Note: For more information on how to work with DNS on domain registrar's side refer to the similar article: How to configure name server for domain on registrar's side?