MAIL_DIR (string) The mail spool directory. This is needed to manipulate the mailbox when its corresponding user account is modified or deleted. If not specified, a compile-time default is used. MAIL_FILE (string) Defines the location of the users mail spool files relatively to their home directory. The MAIL_DIR and MAIL_FILE variables are used by useradd, usermod, and userdel to create, move, or delete the user's mail spool. If MAIL_CHECK_ENAB is set to yes, they are also used to define the MAIL environment variable.