-By Default, MS CRM allows you to create duplicate detection rule based on a criteria selected by you (name or e mail for example if we are working on the contact entity) .
-If the user tries to enter a duplicate record the CRM will shows a pop up which tells the user that this is a duplicate one but the user still has the ability to click save and save it. !!
-The first solution which jumped to your mind is to detect the duplication at the a plug-in and then prevent the operation but this is a hard solution specially if you will implement it on every entity.
-The Best Work around is to disable the “save” button at the pop up by the following steps.
1. Navigate to your CRM instance on your app server.
2. Navigate to \CRMWeb\Tools\DuplicateDetection\ViewDuplicates\
3. Edit this file in Visual Studio or Notepad.
5. Save your changes.
Enjoy 🙂 !