We just got a Xerox 3600N and are having problems printing multiple envelopes through Stamps.com. I'll tell stamps.com to print 50 or 100 envelopes, but the printer only prints one at a time. After about 7 or 8 seconds, the Xerox will flash the red light to prompt me to continue. When I press the button, one more envelope prints, wait 7 or 8 seconds for light and so on. AFter working with me for some time, Stamps.com support's only suggestion was to install an HP driver. My IT guys won't consider that as they say that would likely impede other printing capabilities. Any suggestions??