Aspx page

<asp:TextBox ID="txtEmail" runat="server" onClientClick="validateEmail()"/>

<script>

Function validateEmail()
{
var reg=/^([A-ZaZo-9_\-\+\@([A-Za-Zo-9_\-\.])+\.([A-Za-Z]{2,4})$1;
var mail=document.getElementById("txtEmai").value;
if(reg.test(mail)==false)
{
alert('Invalid Email Address');
return false;

}
return true
}


</script>

The above code is used to validate email Format

Thanks

Sreejesh