eLearning Series
If you are having your outgoing email blocked by ISPs like Comcast that perform port 25 blocks, or can’t send out through your server because you’re at a wi-fi location, this fix may be for you.
Please note that this may not work on all servers. Please proceed at your own risk. Please also note that this fix may not work if the server is rebooted in some cases (you’ll have to do it again).
If you’d like us to help you with this, we can help on an hourly basis (fill out the contact form at the bottom of the page).
Port 25 Block – Server Fix: What you want to do is basically map an alternative port (say 625) to the normal port 25 process. Your ISP or wi-fi location is unlikely to block traffic from an obscure port. Here’s the command (again, we recommend extreme caution, as you can blow up a server easily with a typoooo or mistake): SSH into the server using a program like Putty.
SSH Terminal Session (logged in as root): iptables -t nat -A PREROUTING -p tcp –dport 565 -j DNAT –to-destination :25
This should do it. Good luck!