BuddyPress.org

Hello. I found out that somehow the email function of the WordPress doesn’t work with BuddyPress. For example, notification for new comments on posts come to my email from address noreply@www.mydomain.com .
But when new users want to register for my site, they don’t receive activation email. I don’t know how to isolate my problem. My URL is http://www.screenshotquiz.com