Comcast SMTP Workaround

[jasonB221]

So I've been trying to set up an email server on my home network. Unfortunately, I am stuck with Comcast and they block incoming/outgoing port 25. I've managed to get outgoing email working by using the relay they provide, however, that still leaves me with having to figure out incoming emails. My idea was to use iptables on a remote VPS I have, and redirect incoming emails to that server on port 25, use iptables to redirect incoming port 25 to my home network port 35, and have my home router redirect incoming 35 to port 25 on the email server.

I set my mx records to point towards the VPS and I have this iptables rule already set up

iptables -t nat -A PREROUTING -p tcp --dport 25 -j DNAT --to-destination <my public ip>:35

If I telnet directly to my IP on port 35 from outside my network, it goes through to the mailserver. However, if I try to telnet to the VPS on port 25, it hangs. My guess is because I have no return iptable information provided. And the main problem: emails still aren't going through locally.

 

If anyone has any ideas on what I'm missing, or if what I'm trying to do is possible/makes sense, please let me know!

[unijab]

You trust the relay of your ISP?

[jasonB221]

9 minutes ago, unijab said:

You trust the relay of your ISP?

I don't trust them very much, but I don't see any other way around this. Their relay provides enough of a workaround for now, and I can always add a layer of encryption on top later.