Moodle - Sent Email Confimation Considered as Spam

My friend (creating [his project using Moodle][1]) asked me about how to prevent/exclude the sent email confirmation from his Moodle project to being classified as spam on new user's email. I cannot answer him because i am not that great with Moodle. Can anyone here help him? Answers will greatly be appreciated. Thanks. [1]: http://technopreneur.fttgraphics.com