When you got the new email address and changed ISP's, you needed to create a new mail account for that new existing email address.

When a mail account is created there are many preferences setup to be able to manage and run that mail account. Trying to track down and modify all of those within the either the config editor or prefs.js is not only time consuming, but you could easily cause further problems if any error is made.

So I suggest you fix the original account by reentering all the old data. Then create a new mail account for the new exisitng mail address.

• File > New> Existing mail account.

or

• 3bar menu icon > New Message > Existing Mail account.

when you have both mail accounts in your left folder pane, you can choose to move any wanted emails from the older mail account into suitable folders in Local Folders. This will save a copy of emails.

Then you can delete the old account, leaving saved emails in Local Folders and only one new mail account.

To remove mail account:

• Tools > Account sEttings
• select old mail account
• click on 'Account Actions'
• select 'Remove Account'
• click on OK

Thanks! I didn't remember the old data (ports, password, etc.) to recreate my wife's old account from several months ago and with a different ISP - I'd written it all down but it was lost in a house fire - but you did put me on the right track. I created a new (sub?) account via File > New > Existing Mail Account with the new info, verified it was working, and then deleted the new sub-account. Now the old one works properly. Duh. This one goes into the "weird fixes" file!