My company is a Google Apps for Enterprise reseller so we have to plan, implement, support, and figure out work-arounds for our clients. We use it in our business, too.
We need a forwarding-only address to send mail to an external system for processing without having to pay for an additional user in the system. While there’s not a direct way to do this, using the Google Apps Groups feature (not to be confused with Google’s Groups property which provides discussion/forums) you can work around the issue. If you’re familiar with Exchange, Groups is the Distribution Group equivalent.
Creating Your Forwarding-only Address
First, log into your Google Admin panel and click Groups. Then, click the Create group icon.
Enter in your new address’s basic information. If this is a public e-mail address, make sure Access Level is set to “Team” and “Also allow anyone on the Internet to post messages” is ticked.
Add the address to forward to in the Add new members box and hit Add. (Not “Add all users in this domain”; I automatically go to that box since that’s usually where a Save box is.)