Cron jobs don't send email

Hi all,

I'm using webmin under CentOS 6.5 to create the cron jobs for ES, ED and EB.
The commands are something like these:
/usr/bin/wget -O /dev/null "http://hocbinhdan.com/index.php?option=com_easydiscuss&task=cron"; >/dev/null 2>&1
/usr/bin/wget -O /dev/null "http://hocbinhdan.com/index.php?option=com_easysocial&cron=true&phrase=mycron"; >/dev/null 2>&1

Af the the crons run, the email activities in back-end show that the emails were sent but I cannot receive them. Mark advised me that it may relate to email config bug I have no idea about it.
Could any one help me?

Thanks,
Giang Anh