This sounds like you may have uninstalled Thunderbird some time ago but never removed all the profile folders.

Then you installed Thunderbird again and it has picked up the old profile. In which case it should have located the old gmx account.

But you say "When I try to update the gmx.net account", but it would only offer that message "Incoming server already exists" if you were trying to create a New>Existing mail account for the gmx email address.

When you start Thunderbird, does it auto show you the old account name in the Folder Pane? Is the old/original gmx account visible in the 'Account Settings' ?

Thanks for getting in touch, Toad Hall. I left the old account in TB, which I have continued to use daily for other email accounts. The gmx.net email address that I have been accessing through another email program still appears in the folder pane--with all the old emails. It is also in the account settings. That is where I was trying to enter the current password when I got the message. What should I do? I think it may not be necessary to keep all 18,000 old emails. My main concern is to get TB working again as my only mail program. I forget exactly why I changed it--I think because TB no longer supported yahoo mail and it seemed to make sense to use another mail program for personal accounts but keep TB for business accounts. Now I'm ready to renounce yahoo mail.

OK. It is probably still using an out of date stored password.

Try this:

• Menu icon > Settings > Privacy & Security
• Scroll to 'Passwords' section
• click on 'Saved Passwords'
• click on 'Show Passwords'

You will see two lines for the account. either 'mailbox://account....' or imap://account... and also smtp:// account....

• Right click on each line and select 'Edit Password'
• completely clear all the contents and then carefully type in the new current password.
• When finished click on 'Close'

Note, the alternative would be to select and Remove those lines - but it is worth trying to just edit password first.

Exit Thunderbird and wait a few moments for background processes to complete. Start Thunderbird.

It should auto use the new passwords you entered and connect - assuming all other server settings are correct.

If you removed those stored passwords then you should get prompted for new password. In which case remember to select the 'Remember PAssword' checkbox before clicking on OK

Unfortunately it was not clear to me that each mail account would have 2 password lines (dumb!). So I deleted the second line for two different accounts! Now I am not able to reconstruct them.