Thunderbird login to email server hangs with message: "looking up posteo.de"

I'm on an up-to-date Ubuntu 24.04 on a ThinkPenguin J4 laptop with 25G of memory, using latest Thunderbird 154.0 [Mozilla Thunderbird Snap for Ubuntu - ubuntu-snap-build - 1.0] This has been a problem even before the transition to 153-154 (very slow login), but now it is almost impossible to log in. I click on Thunderbird icon, it comes up and asks for my password. After PW is entered, it hangs with the above message for almost 2 minutes before my emails show up. Ping to posteo.de is immediate on this same laptop, and K9-Mail on my Droid works fine. Thanks.