Mail and Messaging Guide
Chapter 4, Managing mail with MMDF
The postmaster address

The postmaster address

Every host must provide a special postmaster mailbox (required by RFC 821/822). You can either define an alias that maps postmaster to an existing user on the system (a person responsible for mail administration) or you can create a postmaster account to which mail inquiries and problems can be directed.

The MMDF Configuration Manager provides an opportunity to set up an alias.

NOTE: It is best to map postmaster to a local user because the address is simpler and, therefore, more likely to be a valid address. Also, with a local user, delivery of the message does not depend on a network connection that might be malfunctioning and therefore responsible for the original mail problem.

If the person responsible for mail administration at your site changes, change the postmaster alias accordingly.