Currently, an email is not sent to the user by clicking [Forgot your password?] when same mail address in other [Contacts] record is used on [Email] field in [Contacts].

When using same email address between [Contact] records which are used for Portal and [Contact] records which are not used for Portal, the user cannot reset Password by himself.
It would be convenient if password reset email is sent to the user even whose email address is used to other [Contact] records.