If your mail server supports Sieve mail filtering language, you can use a simple text scripts to enable powerful mail filtering and management that is applied directly on server-side. This allows you to create filters that will works client-independenty (a true saviour for those enforced to use Microsoft Outlook).
Sieve has no variables, and no loops (but does have conditionals). Thus, it is limited to simple filtering operations.
But that is enough for:
- developing simple anti-spam system,
- managing and organising mails, but auto-moving incoming messages to corresponding folders,
- rejecting certain e-mails automatically (i.e. if they're too big or contain invalid attachment).
Here you will find some general info and a few simple script examples.