If the account is IMAP, you've lost nothing. Just reactivate the account. If POP, you may have lost all messages downloaded to date.

Thank you for your help. The incoming server on the account is a POP server. The outgoing server is SMTP. The account was not deactivated, it was deleted, and the profile seems to have disappeared. Sounds like I am up the creek without a paddle?

If you didn't check the box to remove the mail during the account removal, it's possible to recover the mail:

https://kb.mozillazine.org/Recovering_deleted_mail_accounts

From your words, I infer you just deleted from Thunderbird, not from the email provider. If true, that means you lost what has been downloaded, but the account is probably still there with undownloaded/new messages. You're right,thought, about the ones. In the future, should you want to deactivate a POP account, my suggestion is to first copy the messages to local folders.

Thanks again, David. Unfortunately, I always set up my email accounts to delete emails from the server once they have been downloaded to my pc. I do back them up locally on a separate hard drive. But if the solution is to re-download from the POP server to my PC it's too late.

Thanks, SFHowes. I will check this out.

Thanks again, David. Unfortunately, I always set up my email accounts to delete emails from the server once they have been downloaded to my pc. I do back them up locally on a separate hard drive. But if the solution is to re-download from the POP server to my PC it's too late.

Then you can restore from your last back-up, right?

Rick -- I've been looking for them in the backup, and I can't find them.

However, I think I have found a utility that can undo the deletion. I'll know in 30 minutes or so.