"Temporarily" Blacklisted

@XfinityAbel​. Thank you for responding to my request for help. Coincidentally (??), about 5 hours after I posted my original help request, I started (magically) to get email delivered to me on my Thunderbird email Client. As many times before when this happened, I did nothing on my end...all of a sudden (for whatever reason out of my control), it just started to work again. As I mentioned in my original help request, I am an old guy who does not sync several devices, so POP is fine for me (I only look at email on my local laptop). I did, however, look at the URL you mentioned and did not see anything that I have not already done in the past. Again, for whatever reason, I get blacklisted. That lasts for a few days (this time a week), and then it magically cures itself. I give Comcast LOTS of credit for allowing me to keep their domain while no longer a customer (Comcast does not offer service where I currently live), but I wonder if this is a way to "nudge" me to look for other email providers (I have NOT transitioned to Yahoo...I am not a big fan of their platform).

@user_45tgi4 I am glad to hear that it is working now, and I do understand that you prefer not to migrate to Yahoo. Hopefully everything will remain working now, and you will not have any further issues getting those emails! Was there anything else we could help you with? 

@BruceW​. Thank you for responding to my request for help. As a (recently retired) 40 year Software Developer/System Administrator/System Tester, I completely agree with your assessment about the "quality" of error messages coming out of Software these days. There was many a review where I would make the comment about the text string not matching the error condition, and was promptly ignored! I have since learned there is now a word for that - "ensh**ification". Regardless of the error message, however, the problem is still that the Comcast Servers are rejecting my query. I also agree with you that it's Cox who really controls the IP address (I have my router set to to dynamically get it from Cox). What I do not understand is why Comcast and Cox cannot "get along". Cox is a major ISP, as is Comcast. I am not sure about Comcast, but Cox has Class 1 IP addresses. Why does Comcast reject requests from (what should be) a well-known IP address? Further, if Cox always uses the same (set of) addresses (and it does), why does Comcast sometimes accept and sometimes reject my email queries? I realize computing is VERY complex these days (with all the Security/etc measures that did not exist when I started), so that may explain the inconsistencies.