Data security in a mobile e-mail service

A method for conveying e-mail traffic between an e-mail server and a mobile terminal which has an e-mail address (A) under the e-mail server and permanent terminal identity (B) and a temporary identity (D) in an access network. A connectivity function is operationally coupled to the e-mail server and the access network. The connectivity function encrypts e-mail traffic to the mobile terminal and decrypt e-mail traffic from the mobile terminal, by using encryption information (C). The mobile terminal generates (-) a service activation code which comprises an identifier (D) of the mobile terminal, encryption information (C) and checksum information. The service activation code is conveyed (--) via a secure channel (-) to an authenticating terminal, from which the identifier (D) of the mobile terminal and the encryption information (C) are conveyed to the connectivity function.