RT3.0.0 - FROM lines in Tickets aren´t OK

I’m a newbie to RT.

After successfully installing RT3 I tried creating tickets, which works

The thing is that Emails to the clients have set the sender
wwwrun@hostname.my.domain, which is the user the webserver is running with.

This also happens with comments etc.

How can manage to set the sender to the email-adress of my RT-System?

Thanks in advance for your kind help

Klaus Hoffmann EMail: klaus.hoffmann@s3-med.de
HOFFMANN Consulting Tel.: +49-7161-989464
Unternehmensberatungs GmbH Fax: +49-7161-989466
Zeisigweg 1 Mobil: +49-170-2033183
D-73054 Eislingen Mobilfx:+49-170-132033230