Is there any way by which i can change the email field in the User Object to a formula field in salesforce?

Hi Saurabh,

You can populate the Formula field value to email field of User by using Process Builder.

• Navigate Set up -> process builder -> new
• Enter the process name and select "A record changes"
• Specify the object name as User and select the start process as when a record is created or edited
• Define the criteria and select No criteria -just execute the actions
• In the field values, select field as Email and Type Reference. From the Value , search for the formula field name. i.e. National Email
• Activate the process builder.