I am a ProAdvisor and have discovered a workaround for this problem. I have also reported the solution to QB under INV-0671.
We are operating Windows 10 with 2019 QuickBooks Enterprise with the Manufacturing module installed with multiple users. The problem typically appears when a user turns on or restarts the PC, which resets the startup files.
When QB "freezes" while sending an Invoice or Estimate, do not CTRL-ALT-Delete. This can damage the database requiring a Verify/Rebuild Data. Instead, open Widows Task Manager, select QuickBooksMessaging and End Task. (NOTE: be careful not to end any other programs as this may require the PC to be restarted.) This action will release QB to continue as before. QB will automatically reopen QuickBooksMessaging. Next, when you attempt to send the email again, the New Email window should appear in Outlook.
As background information, QuickBooksMessaging is used to communicate with other users, connects to outside applications and monitors who is logged onto the database in multi-user applications. When logging on to QB and you receive a message that the user is already logged on, this is the culprit, due to an improper shutdown. Follow the same procedure above to resolve and logon.
