I have had this same issue trying to email estimates, invoices, payment receipts, etc through QB Desktop!  It is infuriating.  None of the steps they say to take helps the situation.  We have used QB for over 20 years and have no desire to switch to QB Online - especially due to the negative reviews.  Intuit takes away the Scan Manager Feature and now will not allow the desktop version to be compatible with Outllook - yet they want to increase the annual fees for QB Desktop and QB Payroll.  This company used to be great but now they are pathetic.