There is a newer issue of thie ISPmail guide available if you are using Debian Jessie!
Per request I have added a section to the Wheezy ISPmail tutorial about how to track last logins with the Dovecot mail server. This can be useful if you operate a semi-public mail server and want to expire email accounts that have not been used in a while. (Not to confuse with the expire Dovecot plugin whose purpose is to automatically delete emails in certain mail folders like the Trash.)