I'm having the same problem and, frankly, I'm so frustrated with QB's inability to focus on this problem and fix it.
For what it's worth, here's a new guess as to what may be happening, and maybe you have some actual techs who can look at this.
- The interface that QB uses to send mail is the "mailto:" link, and it does it exclusively through Internet Explorer, and not through any other browser.
- In the newest implementations of IE, the default helper programs for processing such requests aren't programs at all. They're all "apps" that you pick from a list on the Microsoft store. Even if you choose the "Office 365" choice - as one of the suggestions is this or another thread says - it doesn't point to the Office 365 desktop program. It points instead to the app, which is web-based.
- What you want is for the helper program to be the outlook.exe program that resides on your desktop, but IE doesn't seem to let you do that anymore.
Fix this, please! It's awful. If you need to allow the use of Firefox or Chrome to work around it (instead of IE or Edge), please do. It's driving us nuts.
