Hello,
It seems little odd in my case, I have enabled SMTP_BLOCK so that no script can send mail directly. Have also enabled SMTP_ALLOWLOCAL but all mails are blocked. Even notification sent by CSF itself is blocked. In /var/log/maillog seeing message that connection to port 25 is refused for each mail.
Even mails from usermin are blocked. If I disable SMTP_BLOCK , all starts working.
What am I getting wrong here ?