Abstract: Described is a system and method in which client-side tracking mechanisms allow a computing device to efficiently decide which messages need to be downloaded from a server for subsequent filtering evaluation, and request only those messages. For example, the present invention may be used to limit a download of POP3 email messages to those received in the last n days. When a message is downloaded that does not meet user-specified filtering criteria such as a date window, the message data is discarded, but the state of that message as not meeting the criteria is preserved in an already-checked table. On a subsequent data request, the received list of unique message IDs is checked against the main message store and the checked table, and message data only downloaded if the unique ID is not found. Messages that are not listed are removed from the message store or the checked table.

Abstract: Described is a system and method for filtering messages received by a message-handling program, that leverage the existing message-handling architecture of computer devices to trigger events and perform other actions instead of (or in addition to) displaying the messages to users. One or more rule clients, e.g., COM objects, register for processing messages. When an appropriate message is received, the message-handling mechanism passes the message to a rule client. Depending on how that rule client responds, the message-handling mechanism determines what to do with the message, e.g., discontinue the message. Messages that are not discontinued are passed to another rule client, if any, or displayed in the user interface, if not. Rule clients may be read only, or may have write access, to modify messages. Messages may be hidden from a user by a rule client, modified before being display to a user, or left intact.