On Tue, Jul 16, 2019 at 10:39:57PM +0100, mick crane wrote: > well when I became aware of all this stuff, I thought this is great, > everybody can connect and do what they like, if of course following > protocols. > But you can't do that can you ? you have to connect through a service > provider.
Certain ISPs (primarily those focusing on home customers, and especially those providing dynamic IP addresses) will block outbound connections to port 25 (smtp) by their clients. If your connection comes from such a provider, then, yes, you do have to pass your mail through their mail server, because their firewalls will prevent you from directly connecting to any other mail servers. But if you're not in such a situation, then you absolutely can run your own mail server, although there are hoops you need to jump through to avoid being mistaken for a spammer. Having a static IP in a non-blacklisted subnet and properly-configured DNS pointing back to that IP address are, in my experience, the primary factors. I don't think I've ever needed to do more than that for my own personal mail server, which I've been running since the summer of 2000, and it's been connected on at least 4-5 different ISPs over that time, including both residential and commercial providers. If you want to send mail claiming to originate from other servers, then *that's* where it gets tricky and cumbersome, because you need to properly handle SPF and DKIM restrictions, which you may not have any direct control over. I occasionally have to deal with this at work, and it's never a pleasant experience. -- Dave Sherohman
