Systems and methods for sharing an e-mail address between a host system (100) and a mobile terminal (102) addressable by a temporary wireless identity (122D) in an access network (114). A terminal identifier (122A) is assigned to the mobile terminal (102) or its user. The system comprises a connectivity function (600) and a messaging centre (110) that collectively maintain an association (610, 612) between the terminal identifier (122A), encryption information (122C) and the temporary wireless identity (122D). When detecting an e-mail message addressed to the terminal identifier (122A), the connectivity function encrypts the e-mail message with the encryption information (122C). The messaging centre determines the temporary wireless identity (122D) of the mobile terminal and transmits the encrypted e-mail message to the mobile terminal which receives and decrypts the encrypted e-mail message.