These articles are complete and authoritative documentation of Kolab Now services.
Incoming mail is automatically processed by the server and handled/organized according to defined criteria. For example the server can be made to move the message to a specified folder, redirect it to another account, send a reply, discard, delete, etc when certain criteria is fulfilled.
Filtering is based on the Sieve language, which means that under the hood all filters are stored as a Sieve script on the server. This interface allows a user to define rules in easy way without the need to know the language.