HP Fax Products — Testing Your HP Fax Machine with the HP Fax Test Service 1-888-hpfaxme (1-888-473-2963). When your fax is received by the HP Test Fax Service, we will generate a return fax to you within five minutes confirming that we received your fax. This verifies that you can both send and receive a fax with your fax machine.
Send a test fax to 1-855-FX-CANON (1-855-392-2666). 3. Once our service receives your fax, a test page will be sent back to the fax number programmed into your machine. This process generally takes 2 to 3 minutes. From Google search results.