You are running an email server configured with the default settings. In which directory will you find the delivered mail for the user foo?

A.
/var/spool/mail

B.
/home/foo/mail

C.
/var/mail/spool

D.
/var/users/mail

Explanation/Reference:
Defined in the FHS. see http://www.pathname.com/fhs/pub/fhs-2.3.html#VARMAILUSERMAILBOXFILES

In newer distributions /var/spool/mail is a link to /var/mail. This directory contains all delivered (but unread) mails for each user.