21. A non-transitory computer readable storage medium storing one or more programs for execution by one or more processors of a server computer system, the one or more programs comprising: instructions for receiving a plurality of messages directed to a user, each message having a unique message identifier; instructions for generating a plurality of conversations, each conversation including a respective conversation identifier and unique subset of the plurality of electronic messages; and instructions for responding to a search request from a client associated with the user, the search request including one or more user-specified query terms, including: instructions for selecting a list of conversations from the plurality of conversations in accordance with the search request, each conversation in the list including at least one electronic message that matches the search request, at least one conversation in the list comprising two or more electronic messages; and instructions for transmitting over a network to the client for display the list of conversations in an order determined in accordance with first predefined criteria, each conversation in the list being represented as a single item in the list of conversations, at least one of the conversations comprising two or more electronic messages, wherein each item representing a conversation having a plurality of messages has an associated icon indicating the number of electronic messages in the conversation.
23. The computer readable storage medium of claim 21 , wherein the respective conversation identifier is based in part on information other than a subject reference of the message.