You shall have most luck if you use the smtp server of your ISP.
For instance, I am on NTL broadband. I set email address to my yahoo account and smtp to smtp.ntlworld.com. As an NTL subscriber, I am not required to provide a username or password. Your own ISP may have different rules, but I believe it is quite rare for them to require a username and password from their own customers.
Hope that helps
Andy