8. The method of claim 1 , wherein: the conversation search query includes a conversation-search component and a message-search component; and selecting the one or more matching conversations includes: identifying a set of conversations that each include a representative message matching the conversation-search component; and identifying, as the one or more matching conversations, one or more conversations from the set of conversations that each include at least one message that includes message terms matching the message-search component.
8. The method of claim 1 , wherein: the conversation search query includes a conversation-search component and a message-search component; and selecting the one or more matching conversations includes: identifying a set of conversations that each include a representative message matching the conversation-search component; and identifying, as the one or more matching conversations, one or more conversations from the set of conversations that each include at least one message that includes message terms matching the message-search component. 9. The method of claim 8 , wherein the search query includes syntax that identifies at least a portion of the search query as a message-search component.