My site doesn't email users after they sign up. I have another MU site that uses this same host and that site is doing fine. My site is on Wordpress 3.2. Not sure whats going on. I made sure the Wordpress settings "Both sites and user accounts can be registered." is checked...No errors produced at the host, emails are not in spam. In fact I used the same emails on the other site and set up user accounts no problem. When you register a new site no confirmation email is sent.