I suggest doing nothing until the change is made and you can see your messages online in the new domain name. I am assuming this is an IMAP account. Once you verify to yourself that the email provider kept everything, you can change the account specifics in Thunderbird and I think TB will then restart.

I wonder if keeping back-ups current before the change would be worthwhile too.

Thanks for the replies. david, This is a POP account on TB. The provider has already implemented the new domain (myctl.net), but is forwarding email addressed to the old domain (q.com) through 12/31/25. I have tested this to/from TB for both domains from a gmail account, and everything went through. So, to clarify my question, Can I change my existing Thunderbird POP account name and email (from username@q.com to username@myctl.net) and retain all existing folders and emails in the changed account? Some server settings would also be changed. Or, do I need to set up a new TB account?

Rick, I would definitely make backups before any account changes are made. Also, I know that MozBackup has not been supported for some time, bit I still use it (1.5.1) successfully. Most recently, I established TB and FF on a new Windows 11 Surface notebook. However, for this account modification, I'd also use the "Creating a backup of large profiles" method. FF profile is small, but TB profile is ~30 years old and quite large.

Doing a backup ensures no problems. Changing server and email address should be okay, but thunderbird will need to restart. Using the old Mozback utility is playing with fire, but if you're happy with it, fine. Your SAFEST approach is to use windows to do the backup. DO NOT use the tools>export menu.

BACKUP

1. ensure thunderbird is not running
2. enter %appdata% in search window on task bar and press Enter key
3. this should open windows file explorer in Appdata\roaming folder
4. highlight the Thunderbird folder and copy to external media

RESTORE

1. ensure thunderbird is installed and NOT running
2. enter %appdata% in search window on task bar and press Enter key
3. you should be in Appdata\roaming folder , copy&paste the exported Thunderbird folder there. This may prompt to overwrite an existing folder of same name. allow it
4. start thunderbird and all should be there

david, Thanks a million for the response. I agree, MozBackup is risky. I'll use the windows procedure you documented for backup and recovery from now on. I'm new to using this forum, but I can see why you are TOP 10! I'll post when I do the account change, but it may be a while. Centurylink has kept everything working for now. FYI, I got my q.com account just after Qwest acquired USWest in 2000 . Yep, I'm old.... Cheers, Greg

OK. let us know if any problems. :)