I mean I deleted the old email account with my provider not just the email as I stated in the first sentence.

added this to original post

I think you will find your provider has not actually deleted the account, so when Thunderbird connects it get the new mail that arrives to that address.

Move all mail to local folders from your historical account and once that is done remove the account from Thunderbird.

I'm somewhat new to Thunderbird. Under the email account tree on the left side bar, there is a local folder and under that is another folder called inbox. If I understand you correctly, the copies of the emails in this folder are on my computer and if I deleted the account from Thunderbird, the emails would be available on my computer.

I just realized I was not clear. Thunderbird is downloading the emails to the old email into the the new email folder. I checked the server settings and everything seems correct.

Remove the old account from Thunderbird as instructed. Yes, the emails in the Local Folder/Inbox will remain available on your computer after removing the account, so make sure you copy ALL the messages you need from the old account to the local folder, then remove the account from Thunderbird.

I will do that. Any idea why Thunderbird is downloading the emails from the old account into the new account?

You probably configured both accounts to use a global inbox folder (a single inbox where both accounts store their messages), or you're viewing unified folders whereby the inbox displays all the messages from both accounts. What you describe doesn't just happen on its own, Tbird has to be configured that way because its default behaviour is different.

You probably configured both accounts to use a global inbox folder (a single inbox where both accounts store their messages), or you're viewing unified folders whereby the inbox displays all the messages from both accounts. What you describe doesn't just happen on its own, Tbird has to be configured that way because its default behaviour is different.

You probably configured both accounts to use a global inbox folder (a single inbox where both accounts store their messages), or you're viewing unified folders whereby the inbox displays all the messages from both accounts. What you describe doesn't just happen on its own, Tbird has to be configured that way because its default behaviour is different.

You probably configured both accounts to use a global inbox folder (a single inbox where both accounts store their messages), or you're viewing unified folders whereby the inbox displays all the messages from both accounts. What you describe doesn't just happen on its own, Tbird has to be configured that way because its default behaviour is different.

I just accepted the defaults when I setup the new account. The only thing I see in common on the two accounts is the server names. The user names are different. And Tbird asks me for the password for the old account when it tries to log in to the old account.

Right now I have set up Tbird not to download the emails from the old account and I have set up a filter to take any emails sent to the old email and move them to a special folder I created for that purpose. This is just a get around until I figure out what I did wrong.

Once I have saved the emails from the old email to a local folder, I will delete both email accounts and then add the new one back again to see if that fixes it.