Perhaps explain what that means to you. Because I struggle with duplication of something that has been deleted and is not there.

These duplications began on 11.23.2023 at 1:01 p.m. The sequence continues to repeat. I delete them, and they come back. The only change is that they were rolling in 30 at a time. Now they come in 13 at a time. 25 X 13 = 325 emails per day. I am not receiving new emails. Please advise.

Have you just left it to settle down?

There are many reasons mail might be downloaded over and over and they vary from IMAP and POP.

I will guess you are using POP as when antivirus programs encounter a malformed email on the server they have a habit of dropping dead instead of doing something useful, so folk get todays or their most recent mails over and over because the antivirus product drops the ball evertime it sees something it can not cope with so things never complete. Usually in this instance the number of mails that are duplicated increases every time Thunderbird connects as new nail arives and the download of the old never completes. The solution here is to log into the web mail and first delete the contents of the spam folder as usually a malformed mail will also be spam. Failing that disable the scanning of incoming mail until you actually successfully get you mail and the server has deleted the item that is making the antivirus croak.

In the case of IMAP, there are server actions that will see the contents of the server folder downloaded again. These are usually one off things that are a result of software upgrades on the mail server (or sometimes a new mail server hardware).

But as I do not know which mail protocol you use I offer the most common scenario for both.