Hi Connection lost suggests your Internet connection was not stable. If you are on a slow, intermittent, maybe rural connection, or are using WiFi or phone data and moving out of range, the connection may be entirely lost or interrupted. Also, if the Internet connections between you and Yahoo, or the Yahoo server itself have connection problems, the same can happen. If you were sending a message when the glitch in the connection happened, Thunderbird lets you know the process was not completed so you can try again. Right now, with the COVID-19 crisis and so many people working from home and trying to connect with information or family, the Internet is under incredible load ... just like when you can't make a phone call and you hear 'all circuits are busy, try again later'. I hope this explanation helps. Agnes

Agnes, many thanks for your assistance! As it happens, this 'glitch' occurs on all three of my laptops; when one goes awry, they all do. I've had this problem for at least a year, long before the virus arrived, and unfortunately my ISP (Frontier/Yahoo) can't solve it. I'll see if I can contact Yahoo directly; they might have the answer. I really hate to give up Tbird, the best there is.

Actually, the only way I've managed to solve it in the past was to reset Win 10 (groan), then download a new Tbird. Don't know why that works, but it usually does. I think it has to do with server password rejection, and there's no way (that I know) of changing the password in the Tbird app.

Thanks again. Mitch

What is the authentication method on the incoming and outgoing servers? Tools/Account Settings, Server Settings, and Outgoing Server (SMTP).

https://support.mozilla.org/en-US/questions/1280043

Hi Mitch sfhowes will fix it if anyone can. However, in thinking about ditching TB, you might rather consider changing Frontier/Yahoo. I do not speak from personal experience, but I see a disproportionately high number of connection issues with that particular provider on this forum. You might search the forum for the term Frontier and see if anything someone else discovered helps you. Good luck, Agnes

SF, here are the data. Thanks for the assistance. This is a weird one.

Possibly relevant: this all seemed to start when I downloaded Outlook to my phone in order to get Frontier mail on the phone. But the Frontier/Yahoo sign-in wouldn't accept the password so I changed the password. The phone then worked fine but Tbird had developed this problem.

May not have anything to do with the issue.

Mitch

When you change the account password, delete the old ones or any oauth:// entries in Saved Passwords, as explained in the link of my first reply.

I would recommend you change the time between checks from 2 to 10 mins.

Did as instructed, thanks. Tbird working again; I copied an older profile from another computer and pasted in this one. Probably not kosher but...

One small problem, the interface is black with white typeface (except the message display pane). Don't know how to change that. I tried options, display, etc., still black. See image. Can you help? Many thanks again to you and Agnes.

Check that the W10 Settings for Colors doesn't have the default app mode set to Dark, which will make TB dark even with the Default theme.

Worked !! Thanks.