Postfix Question (smtp)

Hi, I have Postfix setup (almost SuSE default) which allows me to send e- mails from company network. However, when I am abroad, I am unable to send any e-mails through our mail server because of denied relying (in order to avoid usage of our server as spam engine), so usually I am use web mail or change smtp IP of Internet provider in certain area. The question is how to configure Postfix to allow to send e-mail through our domain from any location? I know its possible to setup Postfix smtp authentication with Cyrus, but this is quite complex. Is there any simple yet secure way? Thanks in advance for any suggestion(s) Andrei