Could you please post screenshots of the incoming server setup for each and also of the SMTP server setups for each?

I have had similar symptoms (two identical identities) since 2017 and lived with it but now I am ready to clean it up. Identity A, presumably the old one, is POP3. I have cleared out all the messages in the Inbox and other folders for that one. It does not get anything new except a random sent message. Identity B is Imap. It is the one I use; it has all the standard folders plus a Local Folder which has its own inbox which never gets any mail. I tried to follow the instructions for deleting a profile but the profile manager showed only one profile which it called: Default. This was before I had completely emptied Identity A so I didn't proceed. What do I do now?

Here is a screen shot of my Thunderbird menu; I am running 102.11.2 (32bit) on a Think Pad

@poincare, you may be confusing profile with account. Both of those accounts are in the same profile. You can delete the unwanted one by highlighting it, rightclick and select 'settings' and then scroll down left side of pane to 'account actions' , which is a menu with the option to delete account.

Thanks David. If I delete the profile, will anything else be deleted, such as addresses?

Deleting an account removes server info. I think it may leave emails if POP, but not confident of that. But your addressbook remains untouched.

David, I meant to say "if I delete the account" will anything else be deleted?