Our ISP wants their customers to switch their SMTP port from 25 to 587. They have only given us a three week notice. Come the end of October, they say they will be blocking all port 25 traffic flowing through their servers, even if they do not host our email.
One idea we have, is to port forward SMTP traffic leaving our network from port 23 to port 587. Is this possible? Would a certificate be required? We have an SSL certificate we have entered into Exchange, but I don't know if that is related.
We are told that many other servers are not setup to accept mail on port 587 (or something to that affect), and that our email would not be successfully accepted. It sounds like we may need a third party service to switch our SMTP protocol back to port 25, and then forward it to servers that expect port 25 traffic.
What options do we have?