When I have CSF firewall enabled, I get an error

When I have CSF disabled, that section works perfectly...

I tried clearing the blacklisted IPS but it didnt help.. the only thing that helps is when I turn OFF the firewall.. Is there any port used by cPanel to check the email deliverabilit?
Is something related to the DNS server not resolving the domain correctly when CSF is ON ?
I am lost here, as web works perfectly when CSF is activated and DNS on leafdns.com is correct with CSF ON....
Thanks in advance guys.