You could add a filter to /etc/postfix/master.cf - for example a shell script that adds a disclaimer to every outgoing mail.
I found something that may be useful for others. http://www.paw.za.org/docs/howtos/postfix-altermime/postfix-altermime-howto.html It uses the packet altermime (only available under unstable.)
mail command in linux Hi guys, [root@hblpk home]# mail Mail version 8.1 6/6/93. Type ? for help. "/var/spool/mail/qavi": 4 messages 4 new >N 1 [email protected] Thu Aug 31 11:56 56/1746 N 2 [email protected] Thu Aug 31 11:57 53/1694 not" N 3 [email protected] Thu Aug 31 11:58 52/1702 N 4 autumnhry@globalmove Thu Aug 31 11:58 53/1763 "Health Alert - normally mail command shows on linux. i can delete mail whichever i require but I cant be able to forward mail and second is i cannot set prirortiy of emails .