Start *Windows'* safe mode with networking enabled - win10 https://support.microsoft.com/en-us/help/12376/windows-10-start-your-pc-in-safe-mode Still In Windows safe mode, start thunderbird in safe mode - https://support.mozilla.org/kb/safe-mode-thunderbird

Does problem go away? Please reply to let me know results.

- If no, then cause is either: bug in Thunderbird, in your Thunderbird profile, your mail provider. Please post into topic the contents of Help | Troubleshooting | copy text to clipboard

- If yes, (still in Windows safe mode) ... start Thunderbird normally

    -- If problem is still gone, then cause is a program loaded during windows startup.  Possibilities include: antivirus SW, virus/malware, background downloads such as program updates
    -- If problem is came back, then cause is likely a Thunderbird addon - eliminate them by disabling each one at a time in Tools | addons | extensions and restarting

- If results are unclear ... possibilities include temporary conditions such as contention from other running programs, downloads related to windows update, ...

Please let us know your findings.

The first time I tried the suggestion it did not work, however, I then ran CCleaner prior to repeating the safe mode process and I am pleased to say that the issue appears to have been corrected. Thank you Wayne Mery, much appreciated, Peejay3640

Sorry to say I have bad news, the problem returned, I decided to reinstall Thunderbird in the hope that this would be successful, unfortunately this has not worked either, so the problem remains. Hopefully someone can find a solution as I have been using Thunderbird for near 15 years and would hate to leave and find a new email client. Peejay3640

Problem solved, Thunderbird's latest update was installed two days ago and the issue has gone away. Deletions and transfers to folders are now operating normally without extended delays. Big thanks to the code writers.

The message "Not Responding..." has gone away, but groups of more than about 5 pause for a considerable time in the middle. One day, I don't know what I did, a toolbar appeared at the bottom of the screen with a "delete" button, when I used that button, Thunderbird deleted faster than Jimmy John's delivers. I have never been able to figure out how to get the toolbar back. Anyone have a suggestion? I am using both Chrome and Firefox Quantum running in separate windows. Firefox is my preferred browser, Google my preferred search. Thanks, and Happy New Year, if at all possible.