"First you need to edit your fanpage. Next go to the "Your Settings" tab. Now uncheck "email notifications" and save your changes. That's all there is to it."
I want to put here something "if you want to change the notification preference, go to header bar of Facebook page and click on notification icon a drop down window opens immediately then click on "See All Notification" and after that a text is visible on the upper header of Facebook page "Notification Settings" Click on it and change your notifications preferences."
GO to the setting and browse a little there, it is present there. I have personally switched off the notifications dont remember clearly. but yes, it was difficult to find for me too.. I had used Facebook help to figure it out.