What you're saying is that anyone/everyone has had access to your email account for he past 20+ years. I doubt that. Somehow, a password was being passed, insecure possibly, but still being used. If you have access to the old computer, thunderbird stores passwords in setting>privacy&security. My guess is that you may need to contact your email provider for a new password.

Thank you David. yes I do have the set top box that I first used all those years back. It has Windows XP on it and naturally I do not use it on line any longer. But I need Windows to access the Cd's that I have purchased from the Hampshire Genealogical Society to research my Family history. I can assure you that I do not have a Password in the memory of that machine. Nor do I have any password in the set top Box that I purchased about 2009 that I had Novatech of Porchester build for me. This is the Box that I first managed to dual book Windows 10 and a Ubuntu on circa 2011. And the Box that last August I tried to update to the latest long term version of 24.04.. And something went wrong with it and I lost Windows 10. So in effect this second machine was my Imap Virginmedia server device. And as I said I did not have a password for this either And when I cared to examine it it too said that the password was insecure. But as said my emails were sent to to my machines and stopped I have flashed up the XP box and this is what it says ( Server Type POP Mail Server, Server Name POP.ntlworld.com Port 110. User name recent cm.edwards1 Then under Security Settings it has this Connection Security . In the box it says None. then Authentication Method in the box it says Password transmitted insecurely. On the outgoing server it has this. In the box it has cm.edwards1-smtp.ntlworld.com. Under the box it has " not specified " and Port 25. My user name and once more it repeats that Under Authentication Method Password transmitted insecurely, and under Password it says once more that there is none. ie Connection Security None.

            Now for all these years I apparently have some 8000 or more emails on my pop3 account. And on my Imap account on the 2009 set top box some 5000 or more emails of which it would seem that some are also from the two different accounts. I have to confess that I myself have taken this to be true. But I can assure you that in those Boxes where you say that I should have saved passwords. There is nothing in either of them. I do not have any passwords because in my ignorance I did not fill them in at the time nor later.
                  I have now flashed up the 2009 Ubuntu set top box  with 24.04.3 LTS  and it says that in Pop I have some 8491 emails and in Imap some 5696 emails. and that on the 11th of March this year I received my last email from Thunderbird  from RootsTech 2025 at 12 minutes past 2300hours.
                  On this other set top box ie about 2009 in the Box that says  Saved Logins. It is empty there is nothing.. And to be honest I am fairly sure that I never filled it in at the time. Sorry but it worked despite not being filled in. Well it  did  until March this year.  Regards  Cliff Edwards.

Thank you David. yes I do have the set top box that I first used all those years back. It has being filled in. ... Well it did until March this year. Regards Cliff Edwards.

You should remove all those information as soon as possible. This is for your own benefits.