Linuxconf has the ability to setup sendmail "masquerading
rules" to rewrite from addresses. While I can't read the
sendmail.cf rules (but then again, who can!?!), my testing
shows that mail sent (w/ elm in my case) from a local
account does not get the from address rewritten. This was
tested with both username@localhost and username@my.FQDN.
*** This bug has been marked as a duplicate of 3202 ***