Steps to reproduce

I'd like to have one e-mail account for 2 records but when I try to modify it as admin I've get the following error:

Email address must be unique, currently used by <ANOTHER ACCOUNT>

Incidental if you press cancel, then you get a NullPointerException (we should fix this).

However if the user itself goes and updates email address using Profile this error does not appear and the e-mail is successfully duplicated.

The customer (in FSH-1299) would like to allow duplicate email addresses and asks that the restriction on admins should be removed (esp since the users themselves can do it).