A good way to check the connectons to mail ports is to use netstat:
# netstat -anp | grep :25 tcp 0 0 0.0.0.0:25 0.0.0.0:* LISTEN 2170/master tcp6 0 0 :::25 :::* LISTEN 2170/master
# netstat -anp | grep :465 tcp 0 0 0.0.0.0:465 0.0.0.0:* LISTEN 2170/master tcp6 0 0 :::465 :::* LISTEN 2170/master
# netstat -anp | grep :587 tcp 0 0 0.0.0.0:587 0.0.0.0:* LISTEN 2170/master tcp6 0 0 :::587 :::* LISTEN 2170/master