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Allow internal network devices to send email with insecure connection

Purpose

If you have some network devices like printer, firewall, and they need to send out notification or report email with insecure smtp connection, please try steps below to get it working without breaking default security settings.

Open additional smtp port in Postfix

Since iRedMail-0.9.3, with default iRedMail settings, port 25 is used for postscreen service, all clients are forced to submit through port 587 with STARTTLS for secure connection.

To support network devices which doesn't support STARTTLS and SSL, we can ask Postfix to listen on additional port for smtp service by appending below line in /etc/postfix/master.cf (on Linux/OpenBSD) or /usr/local/etc/postfix/master.cf (on FreeBSD):

2525      inet  n       -       -       -       -       smtpd
  -o syslog_name=postfix/2525
  -o smtpd_sasl_auth_enable=yes
  -o smtpd_sasl_security_options=noanonymous
  -o smtpd_tls_security_level=may
  -o smtpd_sender_restrictions=permit_mynetworks,permit_sasl_authenticated,reject

• 2525 is the new port number for smtp service, you're free to change it to your favourite port number.
• smtpd_tls_security_level=may allows both secure (TLS) and insecure connections.

Restarting Postfix service is required. After restarting, you can check whether it's listening on this new port:

netstat -ntlp | grep 2525

Now update your network devices to send email through this port number, without STARTTLS and SSL.

Update firewall rules to deny access from external network

It's dangerous to expose this new port number to external network, so you must update your firewall rules to deny access from external network to this new port number.