What is your anti-virus software?

I have Avast which I have been using for several years.

As general suggestions wrt anti-virus software:

Create an exception in your anti-virus software for the Thunderbird profile folder, so that the anti-virus real-time scanner will not scan it. http://kb.mozillazine.org/Profile_folder_-_Thunderbird

Don't let your anti-virus software scan incoming and outgoing messages.

Don't let your anti-virus software scan attachments.

Don't let your anti-virus software intercept your secure connection to the server.

Remove any add-ons your anti-virus software may have installed in Thunderbird.

Keep it working. http://kb.mozillazine.org/Keep_it_working_-_Thunderbird

Also see https://wiki.mozilla.org/Thunderbird:Testing:Antivirus_Related_Performance_Issues#AVAST

Hi Christ1

I am afraid that has not worked, although I don’t like the idea of leaving my email open to attacks.

You'd need to be a little more specific about what hasn't worked.

As I said some of my emails take up to 2 minutes to delete, this does not happen on all message and it does not happen on all those message that come from the same sender i.e. I can delete one message from ebay and it will delete straight away, then others will take 2 minutes to delete. This does happen on messages from other senders. More than that I cannot say.

Let me rephrase the question. What changes did you make to remedy the problem, even if those changes didn't fix it (yet)?

Hi Chris1

I did the following: I disconnected File System Shield, to stop real time scanning Disconnected Mail Shield Disconnected all add-ons within Thunderbird and Firefox Stopped my anti-spyware (Superantispware) from running Stopped Avast from running

Hope this is what you want

Thanks Jules

I disconnected File System Shield, to stop real time scanning

You haven't been asked to do that, and it isn't recommended by any means.

Disconnected all add-ons within Thunderbird and Firefox

Again, you haven't been asked to disable all add-ons.

Stopped my anti-spyware (Superantispware) from running Stopped Avast from running

In general it isn't recommended to run multiple real-time scanners simultaneously.

Please read again the instructions given above. https://support.mozilla.org/en-US/questions/1148345#answer-939609

If you're having difficulties to implement them, please ask in an Avast forum.

To verify whether anti-virus software is the culprit, the only reliable way is to start Windows in 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

Does the problem go away?