I also have this same issue.  This started happening a couple years ago when we upgraded to the latest version (2021) because it was forced.  The issue with the 2MB limit still remains.  You can't claim there is no limit if your software clearly states there is a 2MB limit...

Prior to that, we DID have no trouble emailing larger files as attachments through the "Email Invoice" function inside QB Desktop Enterprise.

This is now the 2nd issue we have found with QB "upgrading" their software.  The first is the issue they created with sending statements.  This also has not been fixed and there are hundreds of posts with the same problems.  Seems like QB is really going downhill.