First step would be to Google IMAP vs POP so you know how each protocol works.

Thank you for replying. I read the recommended articles on an earlier thread for that subject matter while I was waiting for a solution to be suggested. IMAP is what I need for this task. It has been over 18 hours and Thunderbird is still doing the same thing which was not addressed in your answer. So perhaps, an actual solution to the problem could be advanced? Previous answers stating such as Thunderbird naming my local folder Default don't apply in this case.

Since you already know about IMAP you know it is server based. You do not download anything but message Headers and you view the messages on the server remotely. This does not lend itself very well to getting local copies. As for deleting and receiving, Thunderbird sync's messages with the server each time you connect to the server. If you want local copies then move copies of messages into a folder under Local Folders or use POP.

Thank you for responding again. This is interesting because this Thunderbird configuration article says this, "You have the option to choose either IMAP or POP as your incoming mail protocol. IMAP and POP are the standard protocols for retrieving emails. IMAP, the more modern protocol, allows you to store messages on the mail server and on your local machine at the same time. The POP protocol only allows messages to be stored locally. Email providers may provide access by either the IMAP or POP protocol, or may support both. (To get a better understanding of the technical details for both protocols see also Glossary of Terms including types of Accounts and IMAP Synchronization)" https://support.mozilla.org/en-US/kb/automatic-account-configuration

Are these instructions incorrect? See, I'm not stupid, the article clearly states IMAP stores in both places.

There is a folder under local folders with a proper name not "default". This is getting very confusing as it one point Thunderbird claimed to be downloading 381 million emails. if I had saved all my emails ever received from all my accounts since first logging onto the Internet, the total not would be in that margin of error.

So, am I looking at an uninstall/reinstall problem or can I open emails and just hit the archive button? Or is it possible to set up a new account for that email and make the server account POP3 if the above instructions are misinformation?

This is why I suggested you learn how IMAP works. But since you want to base that education on one article, here is the problem with that statement. Yes you can go into Sync and Storage options and select to keep local copies on this computer. If you delete any of those messages on the server directly or from some other device the next time the computer syncs with the server the local copy is going to be removed also. Tho reason that option is there is for time that you use a device that does not have a connection to the mail server you will have copies of the mail to work with. It does not stop the basic principle of IMAP form working like it does. IMAP=Server based. You view messages remotely with your devices. Delete any message from any device and the message is gone on all devices and the server. In the case where you have elected to keep a local copy, the local storage will be made to match the server the next time they sync up.

Maybe you should follow the other links in that article and read the whole story. https://support.mozilla.org/en-US/kb/imap-synchronization

I will thank you again for replying. But I did not read only one article yet since the Thunderbird Configuration article should carry the most weight and be the most correct, period, I copied it to as it said something different, regardless of what is said elsewhere, but I can take quotes from every article read, not that anywhere, including configuration, has given the solution.

According to what you've written, there should be no random deleting as I haven't manually deleted anything since I can't even get a complete download of my emails to read, whether or not they also remain on the server nor have I shut the program down in over 24 hours. Carping at me about the amount read as you are telling me the Thunderbird instructions, which I bothered to read and follow, are inconsistent at best doesn't change the fact the program is not working as intended and requires a solution to be named. All the reading materials agree the emails should be downloading even if only the complete set of headers and going nowhere until action is taken.