Linux mailcompat command
On SunOS version 4, the mailcompat command provides compatibility for the Solaris mailbox format. You would typically run mailcompat to be able to read mail on a workstation running SunOS 4.x when your mail server is running Solaris.
Enabling mailcompat creates an entry in your .forward file, if it exists. If this file does not exist, mailcompat will create it. Disabling mailcompat will remove the entry from the .forward file, and if this was the only entry, will remove the entire file.
To execute mailcompat, log onto the Solaris mail server and enter mailcompat on the command line. Answer the queries provided by the program.
Enables or disables the mailcompat feature.
mailx — Process mail messages.