As an alternative to the alias database, any user may 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, if the home directory for user mckusick has a .forward file with contents:
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 generally using the J option. If you change this, you will have to inform your user base of the change; .forward is pretty well incorporated into the collective subconscious.