keeping your mailbox secure, even with mailx

[mats at forbrk.UUCP]

If someone took the trouble to look at the mailx (for System V)
or Mail (for BSD) documentation (manpage for mailx; one needs 
to go hunting for the Mail Reference Manual for Mail) they would
find that there is a way (set keep in your .mailrc) to tell those 
programs not to delete your mailbox even when empty. In this 
manner, changed mode settings will be preserved, and nobody has 
to change the default behavior of the mail delivery program 
(usually /bin/mail).

Additionally, mailx depends on mail files being mode 660, but
with group "mail" (not your group). This is so that it does
not have to run setuid root to manipulate your mailbox - it
can run setgid mail instead, which seems somewhat safer.

Mats Wichmann
Fortune Systems