What operating system and release are you using? Run `uname -X`.
mail -f /dev/null
Does this dump core? Normally it would print:
/dev/null: empty file
If it behaves normally, I would guess that your mailbox is corrupt in
some unusual way. When you run `mail` with no arguments, it loads your
default mailbox (/usr/spool/mail/[username] or $HOME/.mailbox). Examine