A plurality of pieces of send candidate information are stored (S12). Each piece of send candidate information has sender identification information identifying a sender of an email, recipient identification information identifying a recipient of the email, item identification information (52b and 52c), item information that are associated with each other. The item information includes element values of one or more elements. From among the stored pieces of send candidate information, two or more pieces of send candidate information that have different pieces of sender identification information, the same recipient identification information, and related pieces of item identification information are extracted (S13). The element values included in the pieces of item information of the two or more extracted pieces of send candidate information are compared, and timings for sending emails corresponding to the two or more extracted pieces of send candidate information are set to at least two different timings, based on the comparison result (S14, S15, and S16).