The 'mail name' is the domain name used to 'qualify' mail addresses without a domain name.                             This name will also be used by other programs. It should be the single, fully qualified domain name (FQDN).             Thus, if a mail address on the local host is foo@example.org, the correct value for this option would be example.org.  This name won't appear on From: lines of outgoing messages if rewriting is enabled.

System mail name: