After over 20 years of running my own independent email servers, I've given up. The problem isn't a technical one, or a matter of cost/labor/etc.. The problem is that most people don't use Internet email anymore, and it's become virtually impossible to communicate with them using standards-based Internet email servers.
I've been fighting this for a long time, and managed to get over each barrier that Google & friends placed in front of Internet email, but the straw that broke the camel's back was their declaration that any mail from entire subnets of Internet hosts was spam simply because of where it came from, and my server happens to be in one of those subnets. Since this is a rule written by Google there is no path to appeal, no "allowlist"; if you run a mail server on an address on one of these lists, you are simply fucked.
I could move the server somewhere that doesn't appear to be on "the list", but there's no guarentee that the new address won't be on a new list, and what's worse is changing the address of your mail server gets you put on yet another "list".
So I decided to give up.
The easiest way to ensure deliverabilty to Google's proprietary mail system would have been to move my domains to Gmail, which of course is the actual motivation behind all of this (it has nothing to do withs spam). That wasn't an option so I spent some time looking for alternatives. The criteria was simple but surprisingly hard to meet:
* Deliverability to Google, Microsoft, etc.
* Support a flexible number of domain names
* Provide standard client support (IMAP, etc.)
* Not cost 10x what I'm paying to do it myself
* Not be an administrative nightmare
I settled on IceWarp. It checked the boxes above with the additional bonus of being capable of self-hosting which is a nice "just in case". Over the last week I've been working on migrating all of the domains I manage over to this service and overall it's gone fairly smooth. There was one hang-up which of course only Google noticed resulting in it taking a week for inbound Gmail to work, but even that seems to have resolved as of this morning.
If you are looking for an email alternative to Gmail & friends, at this point I'd recommend IceWarp. I hate that I'm not running my own servers, and so of course I don't love using IceWarp but that would be true of anything. What I will say is that it does the job, it doesn't cost too much and the support team has been excellent in helping me debug some fairly-obscure DNSSEC, DKIM and other DNS-related problems during the move.
If anyone is interested I'd be happy to share the details of my migration experience. I might even write something up here in a few months once the dust has settled and I have a more complete read on how things are working-out.
It breaks my heart what Google has done to Internet Email, but let it serve as a warning to any other technology that hopes to operate independently on the Internet.