Question

How to validate Email in server side . I know how to do that in client side but what about the server side?

Answer 1

You could use a RegularExpressionValidator:

<asp:RegularExpressionValidator
        id="regEmail"
        ControlToValidate="txtEmail"
        Text="(Invalid email)"
        ValidationExpression="\w+([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*"
        Runat="server" /> 

As far as the regular expression to use, just pick one that suits your needs.