I have a Centos 5 box. My server is running plesk. Individual domains are able to receive emails on plesk created email accounts. However, my server is not able to send emails. I tried to use php sendmail and linux mutt command, none of them allows outgoing email. In the plesk panel, I see all emails queued. I also notice the PHP mail function is not sending emails either.
In its firewall iptables I have enabled ports 25 and 587 for smtp.
I have MX 0 and 10 for godaddy's smtp.secureserver.net per https://toolbox.googleapps.com/apps/dig/#MX/
I am really confused why I am able to receive email in my server box but enable to send any email out.