Email Verification Error

Question

Hi,

I am totally new in asp.new, working with PHP (MVC model in Laravel). Now in my new job I have to work in some asp.net websites. First of all, I have to repair an error appearing after a submitting a webform, where our company employees set the data for their business cards.

The Errorr says:

The specific string is not in the form required for an email address.

Any help with this? I know that the email address field is of a hidden type, it says:

           <td>

               <asp:HiddenField ID="hdnFirstName" runat="server" />

           </td>

The value of the field is imported from our AD in a correct form.

While I understand it is because an incorrect validation and I already know that the issue is that this field is blocked with the method called onclick of the submit button, I have no idea where to find the method or where to check the validation of the email field in this case.

Any hints how to get to a point of how to debug this, please?