A server which delivers emails can receive emails addressed to a plurality of transmission destinations including portions that can be arbitrarily determined by a user as a transmission destination of each user. Upon receipt of email from a transmission line, the server extracts the transmission address from the email in a mail accepting unit, and makes a matching between the extracted address and the addresses or address patterns stored in a table within a processing contents storing unit. If they mismatch, the server performs normal mail processing for the user. If they match, the server performs the operations such as destroying the email, returning an error mail message, putting a mark on a predetermined area in the email, or adding a transmission destination address depending on the property of the email. If an encrypted pattern is included in the address, the server performs processing according to the command obtained by decrypting the pattern.