have you spoken to your provider regarding how they can implement that? once they do it, then it is just a metter of adding the new accounts to Thunderbird. I have no idea if your provider can delete your "primary" email address. That is something you will need to discuss with them.

The gods at my ISP say upon threat of dismemberment and death I cannot delete or name a different primary email. To me that means even if went to say Gmail, and stopped using TB, my ISP would continue to forward unwanted spam to my old email address, or is this conclusion incorrect? What do you think?

1. Thunderbird has nothing to do with it. Thunderbird or any other email client checks the email accounts that YOU add to them. If you do not want Thunderbird to check mail for a particular account remove it from Thunderbird.

3. If you have an active email address anywhere, with any provider, that Inbox with that provider will accept messages sent to that address.

3. Not sure why you keep saying "forward." Messages are received in the inbox they were sent to. If YOU forward that email address to another then that is on you.

Thanks. I want to create two new email accounts and eventually end using my present email account. But my present email is listed as the Primary User at my ISP. So is your first point saying that even though emails sent to that address will still be received by my ISP, they will not show up in my inbox in TB if I delete that email account from TB?

Of course Thunderbird will not get mail after you delete the account. After you delete the account Thunderbird will know nothing of it. Deleting will also remove any entries in your folder pane for the account. It will as far as Thunderbird is concerned cease to exist.