A function for recording calls is integrated into estos UCServer. Call recording is realised via a three-way conference with an ISDN card (with a CAPI driver). If a user makes a call and initialises recording, a three-way conference with the ISDN card is commenced on the user's phone. The estos UCServer recognizes the user with the help of the phone number and records the conversation. At the end of the conversation the recording is sent as a file attachment by e-mail to the user. For this purpose the users need to have an e-mail address configured and the e-mail dispatch has to be setup in the UCServer.