Hi DonnyDave,

I'm sorry that I don't understand completely. You say that the messages appeared after re-starting Thunderbird, so they were downloaded successfully and they are present. But you also say that they are lost. How should one understand those two apparently contradictory statements?

"with the option to delete on the server once downloaded selected" -- Then the messages should not be on the server, but you are concerned because they are not?

Is your concern about messages not appearing at all before you re-started Thunderbird? I don't know why they did not appear at first but then appeared later. I also am not familiar with that error message. If you see it again, would you please post a screenshot of it?

One possible explanation for not seeing any messages at first even though the count of messages appeared above the message list is that you had a quick filter set. Re-starting Thunderbird removed the quick filter and showed the messages. This may not be what happened in your case. It's just a possible explanation that should not cause any concern.

And that message appeared *before* Thunderbird retrieved the one hundred messages, so it was not relevant to them?

I'm sorry that I don't understand completely. You say that the messages appeared after re-starting Thunderbird, so they were downloaded successfully and they are present. But you also say that they are lost. How should one understand those two apparently contradictory statements?

On restarting Thunderbird all emails that were there prior to the downloaded emails were present. These are the ones present the last time I ran Thunderbird, a few days ago. This is what was meant by the "existing" adjective ("pre-existing" might have been a more apt word): "Having closed Thunderbird and relaunched, the folder with all the existing emails appeared." The new ones – those received in the intervening period – do not appear in the list and are not on the server either.

Were those messages in the in-box on the server when you last saw them?

Are those messages in the trash now, either on the server or in Thunderbird?

Do you access this account from any other app or device?

Do you use message filters?

Yes. When I checked webmail yesterday there were emails there.

The emails do not appear in the trash, nor in any of the other folders, including those under Local Folders.

The email has only been accessed via webmail and has not been accessed via a client on any other device.

There are message filters set-up for some email addresses which are no longer relevant, meaning they don't apply to the emails received.

Let us hope that someone else can help more than I can.