One of the easiest ways to avoid work is to be certain that whatever the problem is, it isn't the area you're working in.
Granted this allows you to get off the call or reroute the email message, but it doesn't benefit you to just foist the case off and be done with it.
If and when you can, seek out and make note of resources which might be useful when a issue is Not My Department. If you can clarify whose department it is, or direct a customer to a product that might be able to fulfill his needs when your product cannot, that will improve your support chops and the customer's experience at the same time.
