Unable to connect to server

Hi all,

I'm unable to connect to the server to retrieve my e-mails. When asked for the password I get the message - "Sending password did not succeed. Mail server pophost.123.co.uk responded: Login failed."
I use exactly the same settings as on my desktop Thunderbird. Changing from pop to imap doesn't work.
Is there anything I can do or do I need to contact 123.co.uk?

Many thanks for any suggestions.

Rad