Do you have an anti-virus program scanning mail folders? If so, disable that option and see if performance improves. Depending on the AV program, you may want to exclude the TB profile folder. Select Help/Troubleshooting Information and click 'Show folder' to open the profile folder in Explorer (File Manager).

http://kb.mozillazine.org/Profile_folder_-_Thunderbird

https://support.mozillamessaging.com/en-US/kb/rebuilding-global-database

Edit: The profile folder in Win 8 is in the same location as it is in Win 7. You may have to allow the viewing of hidden files and folders (see mozillazine article).

I have windows 8. The two links above seem to not go higher than windows 7. Windows 8 doesn't seem to allow me to get into the files area. So, I guess I'm not understanding what you are a saying.

Why would an anti-virus program stop/slow down a mail program when all of the data has already been downloaded. The problems I'm having with Tbird occurs even when disconnected from the internet.

Why an Anti virus program would stop a mail program... They scan files on access. So every time you change folders and thunderbird opens a new file it scans it.

It takes anti virus programs about 10 minutes to scan a 4Gb file, which is how large your files could be. Then you get the rougue anti virus products like McAfee that cause crashes, slow operation and cause nstemp errors for a year. The usual fix is to exclude the Thunderbird profile folder from scanning by the anti virus program.

In the case of McAfee disabling attachment scanning is also required.

Given the number of reports I have seen today, I am guessing McAfee have a new release. Are you a McAfee user as well?

I do have McAfee. I don't know if they have a new update or not.

I have searched all over my computer (c: drive) and can not fine any profile folders at all, Thunderbird or not. Any idea how to find it (windows 8).

Will try to get "into" McAfee. Not sure what I can get into. Any help would be appreciated.

See my updated reply above about the profile folder.

Here are instructions for McAfee:

https://wiki.mozilla.org/Thunderbird:Testing:Antivirus_Related_Performance_Issues#McAfee

Unfortunately, I don't know how to get to "Disable/delete McAfee Anti-Spam Thunderbird Extension in Tools | Addons | Extensions". I guess I'll have to work on it awhile.

Thanks

Tools | Addons | Extensions

Press F10 and follow the menu.

Tools | Addons | Extensions | F10 doesn't do anything.

There is a McAfee Anti-Spam Thunderbird Extension 2.0 that is disabled. But, unfortunately, F10 doesn't bring up a menu.

Thanks

Follow up: McAfee was the problem. I contacted them via chat. They remotely took control of my computer and changed the settings. Tbird is working well now.

Thanks everyone for your help.