2080 is almost certainly not email related. In the old days of port forwarding, often that would be port 80 being forwarded to another machine on the network, but I googled this port just now and it popped up something about cpanel (Hostmoster) and it's calendar.

So I guess the question is do you have a website hosted with hostmonster and are you using calendars on that site which you have linked to Thunderbird?

Thanks Matt! I have wondered if it could be related to TB's support for Calendars, Tasks, etc. I don't see a way to turn off Calendars though that is apparently the difference between my wife's TB setup that is not showing the annoying security exception.

Does anyone know a simple way to disable checking the calendar? I just want it to be an email client and nothing else.

I asked chatGPT and it said to remove the Lightning extension in addons. I told it the latest version incorporates Lighting into TB. It then suggested the following (below dashed line).

Digging around I found a menu (can't remember where) that allowed me to disable 'this calendar'. It then showed a yellow alert panel saying no calendar was enabled, but sadly it didn't stop the attempts to try to get updates.

I opened up the Developer Tools -> Error Console and I see multiple failures. One is shown below (with it expanded).

            carddav.sync: Sync with server failed.
               syncWithServer resource:///modules/CardDAVDirectory.jsm:645
               onStreamComplete resource:///modules/CardDAVUtils.jsm:189
               onStreamComplete resource:///modules/CardDAVUtils.jsm:189

My wife's Error Console doesn't show these entries, so the plot thickens. How to disable carddav syncing.

chatGPT's response below

While there isn't a simple one-click way to remove all calendar functionality, you can take the following steps to minimize calendar interaction:

Hide the "Today Pane": In Thunderbird's main window, go to the 'View' menu, hover over 'Today Pane' and ensure it's unchecked.

Hide the Calendar and Tasks tabs: You can right-click on the Calendar and Tasks tabs and select 'Close Tab'. This should keep these tabs from appearing when you open Thunderbird. However, please note that this may not persist across sessions.

Remove or Disable Calendars: Navigate to the 'Events and Tasks' menu, then select 'Calendar.' In the calendar tab, right-click on any calendars in the left pane and select 'Unsubscribe' or 'Delete.' If it's a network calendar and you just want to stop Thunderbird from checking it, select 'Offline' instead.

Event settings: You may want to check in the 'Tools' > 'Options' > 'Calendar' > 'Reminders' settings that "Show missed reminders" and "Show alarms for events and tasks" are unchecked.

Lots of excitement about chatGPT. As you have found, AI is as dumb as a rock with the subtleties of context changing over time completely eluding it.

You might want to open the calendar tab and simply right click the listed calendars and select unsubscribe from the menu.

CardDav however are address books, not calendars. So I guess you have synced those as well. Unsuccessfully.

Why not just allow the exceptions? They are the result of you using a different server name to that on the certificate is my guess (you could actually view the certificates involved to confirm that.) It might also be an issue with ESET trying to scan the connection. I did not renew my ESET some years ago because it was slow and no longer unintrusive, simply relying now on Defender and some common sense instead. But I have never allowed AV to scan mail r the Thunderbird profile folders because they mess it up so often. The cure is worse than the disease.