My email address is btinternet.com - using Outlook 2000. Cannot send - error 530 authentication required?

You should contact your internet provider to get the IP number for their SMTP server. It will be a number something like 123.456.78.90. You would then have to enter this in the outgoing server address field in the Properties are in Outlook. You should also check with them about the correct port number for that IP number.