right click the folder, select properties and then repair.

I've been reprimanded about sticking to 1 thread. I tried that as I said in my post but Mozilla wouldn't let me sign in (until now) so I had to start another thread. I'm NOT trying to confuse of clutter...I'm just doing the only thing Mozilla will let me do. For some reason, it NOW let me stick to the original thread. However I still can't follow the suggestion of Matt because it saying another application is open when there isn't any open that I can find.

I have locked the other thread, and am pasting your comment from there below. As you used the same profile to post the other, you were signed in. So I really do not know what happened.

Finally got in to respond to Matt's suggestion. However when trying to right click, properties and repair, this message comes on: "The operation failed because another operation is using the folder. Please wait for that operation to finish and then try again." Even though there are NO OTHER operations using the folder that I can tell since I closed out everything.

Now try the next steps that will help work out what might be locking the access. please report your results back. Click the that helps button in the emails you get, even if it does not, to be returned to the site and the thread,

• Restart Thunderbird with add-ons disabled (Thunderbird Safe Mode). On the Help menu, click on "Restart with Add-ons Disabled". If Thunderbird works like normal, there is an Add-on or Theme interfering with normal operations. You will need to re-enable add-ons one at a time until you locate the offender.
• Restart the operating system in safe mode with Networking. This loads only the very basics needed to start your computer while enabling an Internet connection. Click on your operating system for instructions on how to start in safe mode: Windows 8, Windows 7, Windows Vista, Windows XP, OSX

Sorry I wasn't notified that there was another response to this question. (or if it was, I didn't see it as is happening when I'm stuck using my server for mail.) Trying your suggestion. Says downloading 1 of 400 messages . Still get that same message that caused the problem.

If the email has been deleted off the server and you are certain that it does not exist anywhere in any folder or Archive on server, then maybe it is not actually being downloaded. Maybe the deleted email is reappearing.

If that is the case then maybe there is some corruption in the Inbox file.

Try this: move all good emails out of Inbox to other suitable folders. delete any unwanted emails. When Inbox is empty, right click on inbox folder and select 'compact'.

then right click on Deleted/Trash folder and select to Empty Deleted then right click on Deleted/trash folder and select to compact.