Local users

A local address most commonly denotes a user's mailbox. This is normally located in /var/spool/mail and has the name of the user, who also owns the file. If it does not exist, it is created by Exim.

In some configurations, the group is set to the user's group and the mode is 0600. In these cases, delivery processes are run as the user, and the user may delete the mailbox entirely. In other configurations, the mailbox's group is mail, and it has mode 660; delivery processes are run under a system uid and group mail, and users cannot delete their mailbox files, though they can empty them.

Note that although /var/spool/mail is currently the standard place to put the mailbox files, some mail software may be compiled to use different paths, for example, /usr/spool/mail. If delivery to users on your machine fails consistently, you should see if it helps to make this a symbolic link to /var/spool/mail.

The addresses MAILER-DAEMON and postmaster should normally appear in your alias file, expanding into the email address of the system administrator. MAILER-DAEMON is used by Exim as the sender address in bounce messages. It is also recommended that root be set up as an alias for an administrator, especially when deliveries are being run under the permissions of the recipient users, in order to avoid running any delivery as root.