There are two main ways that Postfix can be configured to create and store a users emails.

• mbox
• maildir (store the emails as files on the Postfix server)

To use maildir, so that emails are stored at /home/username/Maildir/, ensure your Postfix configuration file /etc/postfix/main.cf has the following. This will ensure that when a new user account is created, the new users home directory will contain the mail directory, such as /home/jane.doe/Maildir/.

home_mailbox    = Maildir/
mailbox_command =
mydomain        = example.com
mydestination   = example.com, localhost.example.com, localhost
myorigin        = $mydomain

In this scenario, when creating a new user account on the system using the useradd command, the users home directory will contain the Maildir directory. For example, let's say you create John Doe's user account.

useradd john.doe

However, when listing the contents of John Doe's home directory, John Doe's home directory will be empty (no files, no sub directories).

~]# ls -l /home/john.doe

Let's send an email to john.doe@example.com using the mail command.

mail "Hello World" | -s "Testing" john.doe

The Postfix log should now contain something like this.

Mar 06 11:31:37 post postfix/local[177]: 725FC12D34A: to=<john.doe@example.com>, relay=local, delay=0.03, delays=0.01/0/0/0.02, dsn=2.0.0, status=sent (delivered to mailbox)

And now John Doe's home directory should contain the following sub directories. Postfix creates the Maildir directory and sub directories after the first email is sent to the user.

/home/john.doe/Maildir/cur
/home/john.doe/Maildir/new
/home/john.doe/Maildir/tmp

And the new directory should have one file, for the email that was sent to John Doe.

/home/john.doe/Maildir/new/1448670731.V803I6c004bM330351.example.com

By default, the $MAIL environment variable is probably set to /var/spool/mail/username.

~]$ echo $MAIL
/var/spool/mail/john.doe