outlook now asks for password

Hi
I have been using Outlook Express for some years and it has always downloaded any e-mails on being opened or, if already open, by clicking "Send/receive",
For no reason I can see it suddenly started asking for a password before it would download any e-mails.
When I signed up with my ISP, some 10 years ago, I was given a numeric "customer account password" and an alpha e-mail password I have never needed to use either of these passwords andOutlook does not recognise either of the passwords.
How can I revert to the earlier state of not needing a password, or if this is not possible how do I discover the password?
regards
phil
PS. It is unlikely that I will get the usual reply e-mail so forgive me for any delay in replying.
The ISP that gave me this e-mail account has been taken over by Talktalk who say they are unable to assist with any e-mail program other than their own and would only go as far as giving me a "Webmail" account which is both unwieldy needing log-ins and more passwords and not compatible with my antispam program.