Form validation exclude domains

[ZimZ]

Hi,

I'm using this expression to validate e-mail addresses:

<asp:RegularExpressionValidator ControlToValidate=&quot;txtTo&quot; Display=&quot;Dynamic&quot; ErrorMessage=&quot;Please enter a valid e-mail address.&quot; id=&quot;FromValidator1&quot; runat=&quot;server&quot; ValidationExpression=&quot;^([a-zA-Z0-9_\-])([a-zA-Z0-9_\-\.]*)@(\[((25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9][0-9]|[0-9])\.){3}|((([a-zA-Z0-9\-]+)\.)+))([a-zA-Z]{2,}|(25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9][0-9]|[0-9])\])$&quot;></asp:RegularExpressionValidator>

What I want to do now is also to exclude domains like hotmail.com, yahoo.com, etc.

Can you point me in the right direction?