If the mail is still arriving when viewed in webmail, check for a corrupted message there that might be blocking the rest from downloading, and delete it, and empty webmail Spam/Bulk and Trash.

https://support.mozilla.org/en-US/questions/1158670

https://support.mozilla.org/en-US/questions/1301414

I have done as suggested but still cannot pull down e-mails from webmail.

Who is the mail provider, and what are your settings for that account?

Thanks for your replies. Some further info; I can receive my e-mails via my mobile, but not on my laptop or desktop, which both use thunderbird. The last e-mail I received on thunderbird was on 23rd Aug. I was away just after that and did not check my emails until 26th Aug. That's when I realised e-mails were only coming via my mobile and not through thunderbird. So the problem lies with thunderbird, possibly due to an update that may have happened during that time. Harry

But who is the mail provider? They may have changed their authentication method for desktop clients. Is the account set up on the mobile as POP or IMAP?

Sorry, meant to say; Mail provider is 123-reg. I always prefer to use pop3.

The default for POP is to delete from the server after download, so if messages are read on one device, they might not be available afterwards on other devices. IMAP is a better setup for accounts read on multiple devices.

Thanks for your efforts, but that isn't a solution to my problem. I have used pop3 for years and accessed my emails on more than one device without any problem. This particular problem is not being able to access e-mails at all, from my default server, on any device.

If you can't access the 123-reg account from any device, I would think the settings are wrong, or the problem lies at the server end, as all mail apps cannot connect.

Sorry, I confused the issue there. I should have said any device running Thunderbird. I can access all my e-mails on my mobile phone. As a test, I switched off my mobile so that the only way to access my emails was using my desktop. I then got someone to send me an e-mail from their home. My mobile was still switched off, thus avoiding the pop3 scenario of only being able to access on one device. I still couldn't acccess the e-mail on my desktop. I switched on my mobile and the e-mail came down straight away. This problem has to do with some change that has occurred in Thunderbird.

I don't want to change to imap, I would prefer to try a different e-mail client. Which is a pity because I like Thunderbird and have used it for many years.

All I can think of is that some external app such as antivirus is blocking the connection in TB, or, less likely, the mail service doesn't allow downloads from POP accounts on multiple devices unless 'recent mode' is enabled, as is the case with gmail POP accounts. For the first case, run Windows in safe mode to bypass startup apps, and see if TB works as expected.

OK, I will try safe mode, but this will have to wait until tomorrow. Thanks for all your efforts so far.

I've decided it would be a lot simpler to change to imap as you suggested, which I have done. Now I am even more confused! When I click an email to read it, when I close it, the header disappears. How do I get back to this email to read it again? I've looked in vain for some simple instructions but have yet not found anything. Grateful for your help. Then I will close the post.

Check that you don't have a filter applied in the Quick Filter Bar, i.e. the Unread button, and that View/Threads is All.

Thank you for all your help. Much appreciated. I can now close this post.