Customvalidator OnServerValidate event never triggered - asp.net

Question

I am trying to create a customvalidator to check if an email is already in the database at the point of an user registration. I have seen many similar questions dealing with customvalidators but no answer has brought any avail.
I have simplified the OnServerValidate method to always return false to get ANY sort of response but I am not getting any response. I believe that the method is never being fired. I have come to some conclusion there is some other issue that is effecting the triggering of the event.
Here is the ASP which is inside a contentplaceholder within the master page. There is also a scriptmanager in the master file.
<%--email and confirm email--%>
<td>
<ajaxToolkit:TextBoxWatermarkExtender ID="WatermarkEmail" runat="server" TargetControlID="Email" WatermarkText="Email" WatermarkCssClass="watermarked roundedcorner" />
<asp:TextBox ID="Email" runat="server" Columns="48" CssClass="roundedcorner"></asp:TextBox>
<asp:RequiredFieldValidator ID="EmailRequired" runat="server" ControlToValidate="Email" ErrorMessage="E-mail is required." ToolTip="E-mail is required." ValidationGroup="UserInformation" CausesValidation="True"><font color="red">*</font></asp:RequiredFieldValidator>
<asp:RegularExpressionValidator ID="RegularExpressionValidator1" runat="server" ValidationExpression="\w+([-+.]\w+)*#\w+([-.]\w+)*\.\w+([-.]\w+)*" ForeColor="Red" ControlToValidate="Email" ValidationGroup="UserInformation" ErrorMessage="Invalid Email Format"></asp:RegularExpressionValidator>
<asp:CustomValidator ID="CheckEmail" ForeColor="Red" ErrorMessage="This email already is registered." ValidateEmptyString="true" display="Dynamic" ControlToValidate="Email" runat="server" ValidationGroup="UserInformation" OnServerValidate="checkEmailValidator_ServerValidate"></asp:CustomValidator>
</td>
</tr>
<tr>
<td>
<ajaxToolkit:TextBoxWatermarkExtender ID="WatermarkConfirmEmail" runat="server" TargetControlID="ConfirmEmail" WatermarkText="Confirm Email" WatermarkCssClass="watermarked roundedcorner" />
<asp:TextBox ID="ConfirmEmail" runat="server" Columns="48" CssClass="roundedcorner"></asp:TextBox>
<asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server" ControlToValidate="ConfirmEmail" ErrorMessage="Confirm E-mail is required." ToolTip="Confirm E-mail is required." ValidationGroup="UserInformation"><font color="red">*</font></asp:RequiredFieldValidator>
<asp:RegularExpressionValidator ID="regexEmailValid" runat="server" ValidationExpression="\w+([-+.]\w+)*#\w+([-.]\w+)*\.\w+([-.]\w+)*" ForeColor="red" ControlToValidate="ConfirmEmail" ValidationGroup="UserInformation" ErrorMessage="Invalid Email Format"></asp:RegularExpressionValidator>
</td>
</tr>
And then the server-side script. This has a breakpoint at every line and NONE of them are ever getting hit. So I am assuming that the method is never getting triggered.....
protected void checkEmailValidator_ServerValidate(object sender, ServerValidateEventArgs args)
{
args.IsValid = false;
}
And here is the button to move to the next part of the form. It merely just hides one div and shows another to continue the registration process.
<asp:ImageButton ID="NextButton" runat="server" ImageUrl="images/registration/arrowright.png"
ClientIDMode="Static" AutoPostBack="False" OnClientClick="return false;"
Height="50px" onmouseover="this.src='images/registration/arrowrightgreen.png'"
onmouseout="this.src='images/registration/arrowright.png'" ValidationGroup="UserInformation" UseSubmitBehavior="False"/>
This button is used to move to a second part of the registration process, which I use jQuery for. This is why the OnClientClick="return false;" line is there so the jQuery will run correctly. Is there anywhere around this?
$("[id$=NextButton]").click(function (e) {
//alert(Page_ClientValidate("UserInformation"));
if (Page_ClientValidate("UserInformation")) {
$("[id$=pick_user_type]").css('position', 'absolute');
$("[id$=registration_div]").css('position', 'absolute');
$("[id$=registration_div]").hide('slide', { direction: 'left' }, 1000);
$("[id$=pick_user_type]").show('slide', { direction: 'right' }, 1000);
}
});

Answer 1

When you define the validator group of a validator than you to also define the validation group of Controls which the validator is validating.
So define your textbox like this.
<asp:TextBox ID="Email" runat="server" Columns="48" CssClass="roundedcorner"
ValidationGroup="UserInformation"
></asp:TextBox>
If you didnt define the validation group of your button than define there validation group too/
Edit
OnClientClick="return false;" remove this line to make your button postback. If you dont remoove than your form never submited means it will never send request on server.