Update: Issue below solved. I have no idea how. Suddenly started working a couple of hours after first reporting though I did nothing after posting the original issue. All is good but I don't know why, how, what, or where! I just did a routine windows 11 software update after which my emails on my Comcast account are suddenly not accessible by Thunderbird. Thunderbird loads fine but when I try to sync (or when Tbird automatically tries to sync) with Comcast, I get an error message box: Login to server imap.comcast.net with username xxxxxxxxxxx@comcast.net failed I don't know what to do to try to get Comcast to recognize and permit Thunderbird to resume normal operation. I closed then re-opened my Tbird app and I got a popup to put in the comcast password which i did, however after doing so, I got another popup box with the following: Mozilla Thunderbird ESR Thunderbird Alert from acccount xxxxxxxxxxxx@comcast.net: Temporarily blacklisted IP address -- try again later. Any help greatly appreciated! Currently, my Tbird is nonfunctional. Thanks!