Block an email domain

Hi Everyone,

    I need to block the domain googlegroups.com.  Not to confuse it with groups.google.com.  googlegroups.com is a spam address and i keep getting emails from them, despite having MULTIPLE filters to reject them.  Is there a support email address for comcast I can send the email to so they can block it on their end?  If not, what can i do to make sure these get blocked?  I don't even want to see their emails in my spam folder.

Thank you

Matt