Thunderbird and Quickbooks played wll together until recently. Now Quickbooks doesn't seem to offer Thunderbird as a means to send invoices, PO's, etc. Searching suggests something to do with MAPI, although that may be a rat hole. In the past if we sent a PO or Invoice we had an option to use Thunderbird. Its very important that we do again, we do a lot of business that way. I have no way to determine if it is a Windows 10 problem, a Quickbooks problem or a Thunderbird problem. Any help will be greatly appreciated. Mike