In the latest years, we have been looking for a simple solution to handle e-mail quotas for Postfix for large systems 5000+ email accounts. The quota system available in Linux is good measuring the current quota of an e-mail account but there is not a simple way to notify the users that they have reached the maximum quota. Furthermore when the grace period has passed or the hard quota is reached, users of the mail system can not even unlock their mailboxes. Think that POP3. IMAP or webmail sessions will break as they need to create temporary files under the user's ownership.
A quota hunter
Qhunter aims to provide a simple and creative solution to the problem. Qhunter is one of those solutions designed in a cafeteria and written in four napkins. When the users reach the soft limit of their quota, a rule is inserted in Postfix stopping new e-mail arriving to the account and an e-mail is sent to the user requesting him/her to clean up the account. A large grace period ensures that the user can unlock their mailbox without system administrator intervention
Qhunter also sends daily reminders, tracks which e-mail accounts (virtual) are associated with a system account and notifies the user when the mailboxes are functional again. The code is available in IT46's SVN repository under AGPL licence.
svn co https://svn.it46.se/svn/qhunter/release-1.0 qhunter