close passwd file before setuid -- for paranoia

portability fixes for OSF/1

has to seteuid(0) at the end always; might as well just use
the setreuid trick to simplify the code

write file as recipient user so quotas work properly

add System V comment

clean up a few possible problems & one real bug

typo

arrange for some open files and a reasonable umask

change ultrix version of mkstemp to avoid race condition

fix a couple of other small potential problems

avoid link during locking -- the target follows slinks,
which allows you to create random empty files as root

check ownership of mailbox file

deal with systems that don't have quads

hmm..... make sure no one can predict the lock temp name

restore old mailbox locking (user.lock) so that NFS-mounted
mail partitions have some chance of working

make so it's portable to SunOS and Ultrix. Yes, I know it's ugly.

retry the lstat if the create fails because the file exists,
so we can detect symbolic link replacement

Eric points out that you can compare the stat structures, which
detects if open went through a symbolic link

make the symbolic link race harder to hit by checking after the
open as well as before

don't use __dead here, it hoses portability

ANSI C lint

4.4BSD snapshot (revision 8.1); add 1993 to copyright

bcmp -> memcmp, bcopy -> memmove

try to get the error/failed mail returns right
minor cleanups, major portability hacks

speedup/cleanliness not worth enough, just always write to stderr