Not sure if it's a bug, or me doing something wrong. However, I've tested this on two Debian Edge servers with ISPconfig 2.2.13 on it. When I enter an email address in the "Forward" option in the "ISPconfig's User & Email > Advanced Settings" option, the email does not get forwarded. The email address used to forward to is on the same server, but not the same domain. Again. I'm not sure if this is a bug, or me doing something wrong.