How to set umbraco to accept the same email for multiple members

I have Umbraco 7.5 and I need to set the same email address for different members. How to do it?

My scenario:

I want to have different permissions for different parts (lets say sub-organization) but for a short time the contact person of 2 of those parts are the same. and it can happen again

Solution

In your web config file search for UmbracoMembershipProvider which contains the settings for the member logins. Then set the property requiresUniqueEmail to false and hit save.