An update has now been issued by Quickbooks on this - and the update is ... there is no change. They are still working on a resolution. In other words they don't know what to do?

Having said that things have subtly changed - they now don't tell you when an invoice has bounced. I'm no longer getting bounced email errors and yet my customers are reporting non-receipt.

So Quickbooks way of dealing with this appears to be simply trying to make sure its customers don't know what's really going on?