RBR750 Email Logs

Significant new developments and progress (I'm hoping)...

1.  Email send errors occurred again immediately after I was away from my PC for two hours.  I had NEVER SLEEP set on my power settings, but not on my screen display.  My screen went to sleep, and when it awakes which I forgot about, it too requires me to log back into my laptop via Windows 10 "Hello" sign-in functionality.  I tried to turn off this Require Sign-in option when my screen awakes but Windows 10 is blocking me from doing so with a message that says "Windows Hello is preventing some options from being shown."  (i.e., a separate issue with MS that I am pursuing).  

2.  I then setup a mobile hotspot on my phone and was able to send email through this hotspot while my wifi IP route was blocked.  I set my laptop to go to sleep to see if I could reproduce the email block so as to eliminate the Orbi router from the equation.  Two hours later, when I got back on my PC, I was still able to successfully send email.  I.e., the problem appears unique to my wifi-router-ISP connection to Comcast.

3.  I changed the DNS Server settings to custom on my RBR750 and input the Cloudflare settings 1.1.1.1 / 1.0.0.1.  During the hours when I was blocked from sending email (prior to 6:00 PM CST), this change did not resolve the problem which I presume makes sense because it was my public IP address that was being blocked.  This also reinforced with me that the block was likely occurring on Comast's end.  I posted this finding in my Comcast Support Community thread and finally, finally, the Comcast admin for that site did confirm that they were blocking my IP address and that every day at 12:00 a.m. GMT, the block is removed.  

4.  At 6:00 pm CST (12:00 am GMT) the block on my address was cleared by Comcast.  Then with the Cloudflare DNS Server entries set on my router, I first confirmed that I could successfully send email.  This worked. I then let my PC got to sleep for two hours.  When it awoke, I WAS STILL ABLE TO SEND EMAIL - NO 0x800CCC0F ERROR!!!  I kept my PC powered up all night with Outlook open, the screen went to sleep, and this morning hours after awaking the PC everything is still working correctly (as of 7:57 a.m.).  So, subject to giving this more testing time with fingers crossed, IT APPEARS THE PROBLEM WAS WITH THE ISP'S DNS SERVER AND SOMETHING GOING HAYWIRE WITH MY COMCAST CONNECTION/AUTHENTICATION FAILING WHEN MY LAPTOP WENT TO SLEEP.  The Cloudflare DNS server does not seem to experience this problem.  

For the experts out there, does it make sense that my ISP's DNS Server could cause this problem while Cloudflare's does not?

Thank you for your help.  I would have never known about the custom DNS settings were it not for those on this support forum.  I will be posting again, hopefully after several days, to confirm that Cloudflare DNS is in fact the solution.