How to get a suid root shell with /usr/spool/mail

[utzoo!decvax!ucbvax!unix-wizards]

>From chico!esquire!psl at Berkeley Tue Sep  8 00:46:30 1981
fROM -- Peter Langston (chico!esquire!psl)

Your approach won't work on our system because chown(II) clears the setuid bit.
I thought this was common; you might find it very useful if you're concerned
with security.  (Our system is so paranoid it also clears the setgid bit!)