I've installed postfix in centos and attempted to send an email but I get the error 'Lost connection while receiving the initial server greeting'. The error occurs with gmail, hotmail and my work email domain. The VM where postfix is running is placed behind a firewall with outbound internet connection. I've googled the error message and most of the results point to
domain being blacklisted
lack of ssl
- local firewall
I've just configured a local domain in the /etc/hosts file of the vm where postfix is running - privateip hostname.somedomain.com. Could this be the issue? Is SSL mandatory? Or am I completely wrong in the configuration?