Quickest way is to use cfform validation:
<cfform name="someForm" action="" format="html"
preservedata="yes">
<cfinput type="text" validate="email"
validateat="onsubmit,onserver" required="yes" message="Please Enter
Valid Email">
</cfform>
Finding a lot of regex that work great, problem is that I
need to validate a specific domain (ex. us.mycompany.com).
I've tried manipulating this expression without luck: