Can you post the exact error message or perhaps a screenshot, while blurring any personal information? That would be useful.

Perhaps your email provider has changed their supported configurations?

I'd encourage you to find out if only to rule out that possibility, perhaps also find out if IMAP would be best suited for your needs.

Thanks for your suggestions. Ironically when I went into Thunderbird to take the screen shot, it decided to work, and the last three days emails all downloaded. So now I am puzzled. However the error message when it was there, read; "Unable to establish TLS connection to POP3 server. Server may be down or incorrectly configured. Verify correct configuration in "server settings" in the "Account Settings" window and try again". I checked all the settings and they were correct. My iPhone on the same email address worked just fine. As they say "watch this space" Regards TrevorG

Server issues... which e-mail server do you have?

So... your provider lets you use POP3 but not TLS, perhaps only plaintext authentication (unencrypted, which nowadays is not acceptable anymore).