I actually got an answer that worked today.  I've been using QBooks for 15+ years myself and I do refuse to convert my company to the Online version as the desktop is infinitely better in my opinion (I am a CPA and ProAdvisor).  After dealing with poor customer support in the past, today I upgraded from 2018, which was expiring soon anyways, to using 2021 for my company.  I keep my company on a different year than my clients' companies that we do payroll for because I can't use the time tracking system if I have the same version open for payroll services (ie. can't have a second company opening both using the payroll feature).  Upgrading to 2021 didn't fix the issue.  Previous tech support ended up telling me "Contact your internet provider" as if it is their issue.  Intuit tech support really is hit and miss unfortunately.  Some of their support personnel are great and knowledgeable, others have less knowledge than I do when it comes to troubleshooting problems.  I try to initiate each call with my experience and what I have already tried which, now and then, helps.  But most times they waste 30-40 minutes re-doing all the stuff I've already tried.

However, under preferences, Send Form, we clicked on "QuickBooks E-mail", it seems to be working.  It will use whatever e-mail you have setup under "Company", "My Company".  Previously, I tried Yahoo Mail (with the "one time password" you get from Yahoo mail security, which only worked that time.  After exiting QBooks and opening it back up, it didn't work again.  Same with Gmail.  QuickBooks e-mail has worked after closing out and re-opening the software twice, so it may be a solution.

Hope this helps someone out there.