Fix that works for me until QB gets their heads out of the butt and fixes this:

Issue; If I send an email from QB and just hit the Send button, everything is fine. But.. if I change ANYTHING about the email, such as the recipients address, the moment I try to edit the email Outlook freezes until it eventually crashes.

Solution that works:

As soon as QB creates the email, Save the email as a draft and close it.

QB will release the window and think it's been sent.

Go into your drafts folder, open the email, and edit it like normal and send.

It's a pain to have to do this every time but it works for me until QB resolves this.