Do you mean your CAPS account? Where they take the postage out of your business checking for bulk mail, bills mailed, parcel post, etc? Our postage expense is million$$$ per year. Owner of our mailhouse told me USPS had briefly accepted cards for this and had stopped. As broke as the PO is, I can't imagine them absorbing any merchant fees. I'll double check this on Tuesday.

UPS will not take cards. DHL and Fedex will.