Mail and Messaging Guide
Chapter 5, sendmail administration

Enabling user forwarding (.forward files)

Enabling user forwarding (.forward files)

As an alternative to the alias database, any user can put a file with the name .forward in his or her home directory. If this file exists, sendmail redirects mail for that user to the list of addresses listed in the .forward file. For example, suppose the home directory for user mckee has a .forward file with contents:

   mckee@ernie
   kirk@calder
Then any mail arriving for mckee is redirected to the specified accounts.

Actually, the configuration file defines a sequence of filenames to check. By default, this is the user's .forward file, but can be defined to be more files by using the ForwardPath (J) option. If you change this, you will have to inform your user base of the change; .forward is the standard place to define mail redirection.