I am unable to send emails. The following error appears:
Failed to write to socket: not connected
Also I cannot connect to the 25 port from localhost:
# telnet localhost 25 Connecting To localhost...Could not open connection to the host, on port 25: Connect failed
The issue caused by McAfee Anti-virus Standard Protection policy. It blocks outbound SMTP connection to the 25 port.
Please use McAfee Knowledge Base article to allow connections for your Mail Server in Anti-virus Standard Protection policy or disable this policy at all.