I was pulling my hair for days and finally gave up and came here for any insights...
Server: godaddy.com windows web hosting, running DotNetNuke 7.0.6 (release 1)
Admin > Site Settings > User Account Settings > User Registration: Verified
Host > Host Settings > Advanced Settings > SMTP Server Settings > SMTP Server and port: relay-hosting.secureserver.net, anonymous, SSL not checked
Host > Host Settings > Basic Settings > Host Details > Host Email: something@something.com
I think SMTP server is set up properly, since Feedback module is able to send an email within 10 seconds. The problem is User Registration. It doesn't send an email. It worked before, twice, but, I know all newbies say this, it suddenly stopped working!!
Most frustration is that I really don't know where to troubleshoot. Admin > Event Viewer shows "New User" entry with green, but nothing about email - whether it was successful or not. Where should I start?