[my own workaround, posted in case it applies to someone whose search led here.] No, thanks for the idea but the "recommended settings" did not make a difference. BTW they specify "pop3.comcast.net" as pop server but "imap.ge.xfinity.com" is still the canonical name (CNAME) returned for pop3.comcast.net by DNS (domain name service) tools such as dig, host, or nslookup . That's not a typo, "imap" is actually a substring of the canonical pop server name. There was a fun period around the time of the great port change foulup of 2018 when imap.ge.xfinity.com worked and the recommended servername did not--that is why my settings were pointed to the former. This new problem I posted is apparently related to the configuration of Comcast's certificates. My best guess so far is that a certificate failure appeared on a comcast server recently, and that my email client is fussy about that, but only fussy enough to go through some lengthy renegotiation--every time--eventually allowing the authentication step to proceed. I finally allowed a certificate exception and the behavior is back to normal, so I'm going to leave it to someone getting paid (by us), to figure out the rest. 'hope this helps
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