Using your website's email via Yahoo Mail

Yahoo Mail has provided an easy step by step guide to do this easily.

Your username is ‘youremail’@‘yourdomainname’.‘extension’ e.g. support@ruachost.com, not just support.
The mail server is of the form mail.yourdomainname.ext e.g. mail.ruachost.com if your domain name is ruachost.com.
The port numbers are always correct as at the last time checked. Leave them as Yahoo puts it.

Best of luck.