A communication terminal apparatus capable of registering sender's e-mail addresses upon receiving e-mails including the e-mail address registration instruction information in the subject. The communication terminal apparatus relieves users from the cumbersome task of manually inputting the recipient's e-mail address to the e-mail address storage unit 17 and achieves simple e-mail address registration process in a shorter time. The communication terminal apparatus includes the subject determination unit 16 for detecting the e-mail address registration instruction information from a received e-mail, the e-mail parser 13 for acquiring the sender's e-mail address from the received e-mail, and the sender's e-mail address registration unit 18 for registering the sender's e-mail address of the received e-mail with the e-mail address storage unit 17 where the subject determination unit 16 detects the e-mail address registration instruction information.