Quickbooks does not want to fix the problem because they want everyone to upgrade to the yearly subscription instead of offering what we already paid for with desktop versions. 

This is a terrible issue, drove me crazy for a couple days.  BUT, never give up!  So these are my steps that solved it for me.  Ultamitly QB 2022 will not work with the new Outlook 365.  I installed QB and updated.  Install adobe reader.  Uninstalled Microsoft Print to PDF and Microsoft XPS Document Writer, then reinstalled within the turn Windows features on and off section.  Installed Office 2019, then updated to Office 365 and removed 2019, this is when things broke again.  Within the new Office 365 select New Outlook, then I reinstalled 2019 again.  Now when I have to invoice from QB and select the email button the 2019 Outlook instance finally opens with an email, I then save as draft and edit as I would in Outlook 365.  QuickBooks need an update but they will not fix they want you to go to the online version from what I am seeing.

Thinking about switching away...;

1. GnuCash: GnuCash is a free and open-source accounting software designed for personal and small business use. It offers features for tracking bank accounts, investments, income, and expenses, and supports double-entry accounting.

2. Odoo: Odoo is a comprehensive business management software that includes accounting functionality. It is an open-source solution with modules for various business operations like sales, inventory, project management, and more.

3. ERPNext: ERPNext is an open-source enterprise resource planning (ERP) software that provides accounting features alongside other modules such as inventory management, project management, human resources, and CRM.

4. FrontAccounting: FrontAccounting is an open-source accounting system specifically designed for small businesses. It offers features for general ledger, sales and purchasing management, inventory control, and more.

5. LedgerSMB: LedgerSMB is an open-source ERP and accounting software suitable for small to mid-sized businesses. It provides features for double-entry accounting, invoicing, inventory management, and more.

"8. I closed out of the 2 new windows and went back to the Internet Explorer's Internet Options.

9. Under the program tab I clicked "Manage add-ons"

10. I clicked "Accelerators" on the left.

11. I clicked "Email with Windows Live", then I clicked Disable on the bottom."

Two years later and you just helped me out!

My problem was I installed Thunderbird last week (while keeping the Outlook client) but did not like it, so I uninstalled it and that's when the issues started.  Two separate QB programs had the same issue where I was getting the unable to send email problem.  I had already ran through all of the QB File Doctor steps, the default program steps, and temporarily disabling the firewall.

Thanks, Goodgold!

We have an old version of QuickBooks, Pro Desktop 2015. We had the same problem with it after upgrading to Office 365. We took the opportunity to upgrade the PC to Window 10 from 8.1 to try to fix the problem. The upgrade to Windows 10, removing all apps and personal files, and then installing Office 365 and then QuickBooks failed to fix the problem. A new install of Windows 10 on the bare metal, then installing Office 365 and then QuickBooks failed to fix the problem.

A new install of Windows 10 on the bare metal, then installing QuickBooks and then Office 365 FIXED the problem. In my case, the key was to install QuickBooks before installing Office 365. This solution preserves x64 OS and Office 365. 

I don't know if upgrading to Windows 10, removing apps and personal files, and then installing QuickBooks, then Office 365 would have fixed the problem. I didn't try it.