"By randomly marking your email as spam without any recourse."

Correct.

I'd like to describe how badly this is implemented:

I run my own mail server and I have a 15+ year history of emailing (mywife)@gmail.com.

On a regular basis (mywife)@gmail.com will email me, and I will respond to her email and my response will go to her junk/spam folder.

And there is no alert, no bounce, no notification.

Let's unpack this:

Google (gmail) knows that these two email addresses converse back and forth, regularly, with a 15+ year history. Google knows that their own user initiated this conversation. Google knows my email is a response to their users email. Google knows my address has never been marked as spam/junk.

So, what kind of unimaginably bad heuristics would have to be in employ to allow this to happen ?

To be honest, this wouldn't bother me that much - I don't think google owes me anything and my wife doesn't pay for their service. What makes me so, so angry is that they behave this way without any notification or bounce email.

That's just shitty.

Same here. And I can't even forward mail from one inbox to another because it invariably gets marked as spam. Two mailboxes, same browser, same IP.

> unimaginably bad heuristics

This is every Google product in a nutshell for me. Their "algorithms" are absurdly bad in every category.

Business use of email tends to look a lot like spam and people mark it as such. An appointment reminder or notification that something just shipped is generally fine. Send out mass notification of your holiday sales and that’s going into someone’s spam folder.

> generally fine

So you're saying that anything can get you blacklisted if you're unlucky enough? I think that's the point of the people you're arguing with.

At this point we just need to figure exactly how unlucky.

Not so much a question of luck, sending out sipping notifications that for example include advertising is risky. Sending a high volume of appointment reminders for the same appointment is similarly problematic.

I've never done any of that.

I don’t mean that’s the only way to trip up, there are a lot of unspoken self hosing email rules. Don’t use public data centers, don’t send news letters etc.

My email server is only used as a personal server for a few select friends and family. They absolutely do not send and have never sent anything that could remotely be considered spam. Everything in our setup is picture perfect (SPF, DKIM, DMARC, PTR records, etc). We still can't get email onto Microsoft's servers without it being marked as spam.

Interesting, marked as spam in peoples inbox is different from simply never showing up which is what happens to the vast majority of spam.

See the Digital Markets Act in the EU. It could be a way to force large corporations to cooperate.

While completely abandoning hope for the small players in the process.

Could you expand? Abandoning hope in what way?

You are still hosting it fine. They just decide that you or your messages are suspect.

Also one thing - if people actually want your email they will contact you if they don't get an expected email. If they don't want your messages it is spam.