Abstract: A dummy client accesses each channel of a chat system. When a message is transmitted from a client to a channel, the dummy client checks the content of the message. If the message satisfies a predetermined sentence condition, the dummy client executes a process corresponding to the sentence condition and to the content of each sentence segment included in the message.

Abstract: When a mail address changed, first server receives absence response information containing an old address and a new address corresponding to the change, extracts a mail address of each of other members from a mailing list based on the old address, obtains domain information corresponding to the extracted mail address, and distributes the absence response information to second server specified based on the domain information. The second server receives and stores the absence response information. Upon acceptance a mail from a client, the second server judges whether the mail is directed to the old address and changes the address of the mail to the new address and sends the mail.