problem with the message system

When an user send a new post, I receive a private message from myself, it tell me there is a new message to approve. If I open the private message, I read this communication: "The argument or the message to approve don't exist". So I approve the new post by the admin pannel
When I receive an automatic email from the forum I find the username of the user not activated. What I have to do to activate it?
If I send an email to an user only myself receive the email. Why?
When I receive an automatic email from the forum I find the username of the user not activated. What I have to do to activate it?
If I send an email to an user only myself receive the email. Why?