Entire month of email downloads again

Using Xp and Thunderbird.

Turned on my computer. Clicked on my email icon to get email which might have come in overnight and and got deluged with old email. It looks like every email which I had previously received during this month downloaded again. At last count, there were 730 emails that I had to delete again.

This has never happened before. I would prefer that it not happen again.

I did not do anything different this morning, before the problem. Turned the computer on. After it booted, I clicked on the email icon.

What is the problem? How do I prevent it from happening again?

Sounds like its an issue with your ISPs email server.Have you contacted them for advice?

Not yet, but will do so, now.

Yeah that doesn't sound like any kind of local problem. No email program can download emails that aren't there. This must've been the email provider's issue.