What is your anti-virus software?

My anti virus is McAfee LiveSafe – Internet Security

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

Thank you this has fixed my emails

I had almost the exact same problem. I could read "one" message, but if I tried to go to another, or delete or move any messages, then Thunderbird would lock up. This problem has occurred about once a year for several years.

So, when the problem started again I checked my McAfee settings--- and real time scanning of email attachments was still disabled from a prior year. That had solved the problem until now. So, it had to be something more this year.

The wiki.mozilla link that Christ1 provided fixed my problem as it recommends also disabling scanning of Thunderbird files and folders.

I only disabled scanning of the Thunderbird profile folder; because, that was the only thunderbird folder I could easily locate. (Within Thunderbird go to Help> TroubleShootingInformaiton and then click on the "show folder" tab beside the Profile Folder entry a few rows down.)

My version of McAfee has a different routine for excluding folders from scanning than what is listed in the wiki.mozilla article.

On my 2014 version of McAfee, I right click on the McAfee icon in the systray, then select scan > custom ......McAfee then opens the custom scan page. Then click on the "Excluded Files and Folders" section and click on "add folders" --- and navigate to the profile folder location that you looked up under the Trouble Shooting Information section of Thunderbird "Help."

Thanks, PhilipTx! What a difference. I've been suffering with incredibly slow, hung up, Thunderbird for a long time -- had even temporarily turned off all add-ons without results. Seems fine now. Hope it lasts.

Thanks again.