BT Mail - can't connect to servers, but are they charging extra?

I can no longer get Mail to download onto my iMac which is using Catalina; in fact this was only discovered when I upgraded to a newer iMac running Ventura. The new one would not link to the BT IMAP / SMTP servers, and for some reason now the older one won't, either. Now I'm starting to discover that BT Mail is only available by web browser unless I pay them £7.50 per month, extra. I cannot set up an e-mail account at all, it doesn't recognise the password even though this is my usual e-mail password and my BT.com password. Has any one else encountered this and how did they get round the inability to download e-mails via Mail?