Smart size reduction of a local electronic mailbox by removing unimportant messages based on an automatically generated user interest profile

A system that enables a user to conveniently reduce the size of one or more mailboxes stored on the client computer system. The user can indicate that "unimportant" email messages are to be removed from one or more mailboxes. Unimportant email messages are automatically removed before important ones. To calculate the importance of a message for a given user, message attributes such as users associated with and/or terms contained in the message are compared against a personal interest profile associated with the local user. Additionally, dates associated with the message, such as when the message was added to the mailbox, and/or when the message was last read, may be used to further determine message importance. The size of a message may also be considered when determining whether a message should be removed.