Incoming mail is working great on our server. Our ISP, Verizon, blocks port 25 outgoing supposedly to prevent viruses from sending spam. This throws a huge wrench in my otherwise clean plan to get a mail server going so I don't have to worry about space limitations. Macs can't get viruses, at least not yet >:(
I've heard that there are 3 standard ports: 25, 465, and 587 for SMTP. Verizon recommended that everyone switch their ports to 465 or 587 for Gmail, Yahoo, etc, so it seems like all the commercial email hosts work with ports 465 and 587. Of course, I can't send on just ANY port because it has to match an SMTP port the other mail server accepts. Will ports 465 or 587 work, and how do I switch my server over to those ports (I know how to port forward already)?
You know, now that I think more about it, I think you'd need to have an SMTP relay service outside of your network. Since your server is sending mail to any other mail server, it will have to use 25, because that's where mail servers listen for incoming mail.
The other problem you're going to have is that a lot of servers will reject anything coming from a residential IP address, so a lot of your outgoing mail is going to get flagged as spam, or blocked outright, by the receiving server.
Your other alternative is to upgrade your internet connection to business class, then they won't block your ports. They don't block it to prevent spam getting to you, they block it to prevent spam going out from their IP's, which prevents their business customers from getting blacklisted by the spam blocking services.