US Patent 7228383 System and method for progressive and hierarchical caching

A system and method that allows a user to update the contents of a portable electronic mail account to correspond with the contents of a user's regular electronic mail account, where only discrete portions of the regular electronic mail account are progressively cached in the portable electronic mail account according to a hierarchy with each update operation. By updating only a portion of the regular electronic mail account with each update operation, the service provider can minimize the amount of memory storage and communication expense necessary to maintain the portable electronic mail account, while still permitting the user to access the information important to the user.