Abstract: A computer system having one or more processors and memory receives seed data comprising contacts specified for a draft communication, selects at least a subset of the seed data as a seed set of contacts, and identifies one or more suggested contacts based on the seed set. Identifying the suggested contacts includes: identifying in historical communications in a user account, groups of contacts that include one or more of the contacts in the seed set; generating scores for contacts in the identified groups of contacts, including generating a contact score for a respective contact by accumulating score contributions for a plurality of the identified groups of contacts that include the respective contact; and identifying the one or more suggested contacts in accordance with the generated scores. The computer system sends a contact suggestion based on the suggested contacts for display in conjunction with the draft communication.