You can define filters to manage incoming and outgoing email messages, including Calendar-related messages and Activity Streams. A filter consists of one or more conditions and one or more actions. You can base a condition on a subject, email messages from a specific person, or messages for a particular date. If the message matches the conditions, the specified actions are performed.
You can create filters to do the following:
Note: An email message is evaluated by each active filter, unless you specify that a message is treated only by the first filter that it matches. Usually, you do not want more than one filter applied to a message after the first match because the message can undergo multiple, perhaps contradictory, actions.