Port 587 Open in csf.conf but still blocked

[onlineth]

Hello, I am using a PHP application that sends emails by going through SMTP. The port it goes through to sends emails is 587. I tried to send a test email but no luck. I contacted CPanel about this and they checked csf.conf and saw that it was whitelisted in both TCP_OUT and TCP_IN. They then stopped CSF and testing sending an email and it worked perfectly. They turned CSF back on and then came across the issue again. If the port is whitelisted in the CSF configuration file (by the way, I tried restarting CSF multiple times and restarted the server), what would be blocking port 587?

Thanks for your help,
Thomas

[onlineth]

Wow, I feel stupid! I found this in csf.conf SMTP_BLOCK = 1