This is more an FYI but I suppose if anyone has a low administrative overhead solution to this, I'm open to it.

For the last few weeks I've noticed some problems with email. Certain messages never seemed to arrive from certain folks. Tonight, I was able to troubleshoot it further with the inadvertent help of my bank. The bank sends me one time codes to log in via email. This has worked flawlessly for a while. Today, I couldn't get them. Finally, after turning off TP, I got bombarded with OTP codes.

I also noticed that my issues with MXToolbox checking my domain also largely went away following the disabling of TP.

Threat Protection seems like a good idea but appears too unpredictable to be reliable with near full time attention to monitor it.

I guess I could pass ALL email and rely on the spam filter (as I had before)... I'll think about that... after I've recovered from being so frustrated.

(I figured I'd throw this out there in case others were having problems with select mail being blocked).