Is there a way to turn on the Private Messages for all users by default? Specifically the settings for "ALL USERS" and to make new users have that setting?
Per the documentation below:
The Email Options tab of your user Settings page two settings for private messages:
Enable private message notifications - This is enabled by default. It allows you to receive notifications of private messages sent to you.
Allow private messages from - Lets you choose whom you want to receive messages from. Options include:
None (that is, no one can send you private messages)
Friends only (only users who are your friends can send you private messages)
All users (any user can send you a private message)