when you register, it try to redirect you to the profile page, since the user has not verified the email address yet, they are directed to the login page.
I just tried registering and it worked successfully for me, I received the email, and clicked the verification link, then was able to successfully log in.
If you are getting the email add some addresses but not others, there are two possibilities:
1) The email is being trapped in a spam filter. double check your check mail folder
2A) The smtp server is refusing to relay email for some domains. you will need to work with the host on this one.