What do you mean by "Email Protection"? When you use a web based email account such a yahoo, there is no need for a specific anti-virus for it. Any anti-virus (I personally recommend Microsoft Security Essentials) will protect your computer equally from email attachments and anything else on the web.

If you have some email client (such as thunderbird, Outlook, etc.) installed on your PC, some antiviruses will scan emails in there, but it's not very beneficial.