Did you compact the folder after deleting the messages. If not all you have done is mark messages for deletion. Compacting deletes the messages and frees up the space.

I did compact the folders (did not mention that in my initial posting) but that did not help

what is the exact error message? Is the email account IMAP?

I am not using IMAP; I am using POP. As for the message; it says ".. cannot download message; your disk space is full. Delete unneeded message "

I did delete a lot of messages and moved some to a local folder and got my inbox down to about 9000 messages. Then I was able to download new messages. However, it downloaded duplicates of previously downloaded messages (over 4000 of them). I noticed that not all, but most older messages were duplicated. Now I noticed that "Thunderbird" freezes often and some times I get messages that says "script stopped do you wish to continue?" Now I am in he process of deleting those duplicate messages; a very tedious process. I would appreciate any input on what is possibly going on.

This add-on should help with the duplicates. https://addons.mozilla.org/en-US/thunderbird/addon/remove-duplicate-messages-alte/?src=search

How much free space do you have on your C: drive on your computer? It might be that is where the space shortage is coming from.

Thank you for the "add-on".

As for the disk space on the C drive, I have over 100 GB free.

Not sure why Thunderbird freezes for several minutes especially upon starting.

Freezing is almost always a bad interaction between Thunderbird and something else. This is often the anti virus program, but an product that monitors data over the network, keystrokes disk activity et. al. is seriously a contender.

one common suggestion to to restart in safe mode, both Thunderbird and your operating systems. Thunderbird safe mode excludes add-ons and themes, the operating system safe mode will eliminate anti virus and a host of other possibles.

try the following, including starting Thunderbird in it's safe mode while in Windows safe mode:

• 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

If safe mode for the operating system fixes the issue, there's other software in your computer that's causing problems. Possibilities include but not limited to: AV scanning, virus/malware, background downloads such as program updates.