Hello there. Comphub.

we have read your email. we are going to try to help you.

regards firefox volunteer.

Hello there again. Comphob.

Using the program ccleaner as a program to edit the email program of thinderbird is also a way to do this unnoticed. ccleaner also has a tendency to change and delete parts of the email program without permission.

It is advisable to delete the program, including the other program. reinstall the program in the order of first the email program thunderbird then possibly what you want in this case ccleaner.

if necessary, also switch off some firewalls during reinstallation. use a good antivirus at the moment.

After doing this the thunderbird program will just have to run properly on your computer machine.

Before starting the installation, make sure that there are no problems or errors on the PC machine on which this is performed. Contact us again after implementation.

regards thunderbird volunteer.

It is advisable to delete the program, including the other program. reinstall the program in the order of first the email program thunderbird

This is complete nonsense.

Profile files are stored separately from the Thunderbird program files. The program files are static and do not change (except when you upgrade the Thunderbird application version). Because we store profile and program files separately, you can uninstall Thunderbird without losing your messages and settings, and if something goes wrong with a Thunderbird update your information will still be available. It also means that you don't have to reinstall Thunderbird in order to delete your information or troubleshoot a problem.

Installed new version of Thunderbird.

Are you saying you did uninstall Thunderbird first, and then re-installed a newer version? If so, why? Thunderbird has a built-in update mechanism, which works just fine.

On installation, Thunderbird showed my old email address.

Thunderbird just continues with your existing profile. This is the expected behavior. If you want to start from scratch, create a new profile using profile manager, and start Thunderbird with the new profile. https://support.mozilla.org/kb/using-multiple-profiles

If there is nothing to be kept, you can then delete the old profile.

On the second round, after running Ccleaner, I ran regedit

Letting CCleaner mess with the Thunderbird profile is neither needed nor helpful. It is recommended to disable all options related to Thunderbird in CCleaner.

What was running regedit supposed to do? You should not mess with the Windows registry unless you know exactly what you're doing.

I tried adding a new profile (with the new ISP, did you miss that part?). It screwed Thunderbird up so that neither the old or the new profile worked. That is why I deleted Thunderbird. Yes, I know what I am doing with regedit. I would appreciate it if people that do not know the answer to my problem would stop replying.

I tried adding a new profile (with the new ISP, did you miss that part?).

Apparently I did. Probably because I don't find that piece of information in your OP. You won't hear from me again. Good luck.

The answer is here. https://support.mozilla.org/en-US/questions/1026691 "From the menu bar select Tools-Account Settings Select the account that you want to remove At the bottom of the account list is Account Actions-Remove Account" Then I went to Account Actions again and set up a new account. Done.

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