Relaying Denied Error
553 sorry, that domain isn't in my list of allowed rcpthosts (#5.7.1)
This message is generated when your mail client has not properly authenticated to the outgoing mail server. Outbound (SMTP) mail can only happen AFTER a successful Inbound (POP3) connection has been made - commonly referred to as PoP3-before-SMTP authentication.
Check that SMTP authorisation is selected in your email client. For Outlook/Express, check in go to Tools -- Accounts -- Email -- Properties -- Advanced Service and select "My Server requires Authentication" and "Use same as Incoming".
If you are using some 3rd party internet security program which intercepts email, such as Norton IS, turn it OFF and try again, as mail will not necessarily work correctly with these very buggy applications