i seem like having problem with wp 3.6 email issue.
with 3.6 all email can't be send.
with 3.5 everything work out well.
Both site install in same environment
thanks
check out my live test site.
V3.6
http://penangpropertynetwork.com/?page_id=6
v3.5.2
http://penangproperty.asia/wordpress/?page_id=5