Everybody I know who still runs their email server (you can get Europeans out of Europe, but you can't get Europe out of the Europeans) complains about Microsoft.

I bet Microsoft is single-handedly responsible for 80+% of complaints about email being impossible to host.

In a federated / pseudo-decentralized network, any provider with 10+% of captive users has an outsized leverage on the entire ecosystem. You don't need a monopoly; as long as you have a monopoly on just a few users that others absolutely need to be able to interact with, you can dictate terms to everybody.

Same experience here. We have multiple customers whose servers are in large blocked IP ranges, with seemingly no way to get them delisted. The strange thing is that Microsoft only seems to reject their emails on Hotmail/Outlook.com accounts (free accounts), while accepting them just fine on business accounts. Meanwhile, their “support” tools tell you there’s nothing wrong.

Based on my broad experience, I’d comfortably rank Microsoft as the worst of the major email providers. (I am owner poste.io)

I had experience implementing and debugging mail delivery, so when I chose to run my own server I just opted for a SMTP relay, and never had an issue. I don't know why this isn't the recommended default solution.

> Outlook.com and similar are an anathema to email. This is why they tell you not to run a mail server .

It should be the other way around though.. More people should run their own mail servers so that centralized players cannot control what should be a decentralized communication protocol.

outlook.com and O365 are horrible to deliver to. We regularly get issues where we sent an email it was accepted by O365 but was never delivered to the mailbox. We have one person working at least half the time on resolving stuff like that. And that's from a respectably maintained SES egress with good reputation, DMARC, DKIM configured.

I've had several times where mail from custom domains associated with a business were delivered hours late by Outlook. Time sensitive emails. A guy coming to my office for a meeting called me and said he was downstairs and having an issue with security. Went down and swiped him in.

Four hours later, I got the same message by email. I thought he was back - nope. An email sent at 10am that was delivered at 4pm showed it was from 2pm until I looked at the header and saw sent at 10am and just... chilling out for 4 hours. DMARC was set up for them just fine.

I've had the same issue with my own custom domain, with DMARC set up. A year later, it finally got bumped up to some sort of "trusted" domain for that one place and my emails get delivered the same day now.

Is it SNDS (https://substrate.office.com/ip-domain-management-snds/snds) you refer to as their regular blocklist process?

yeah I see it for them being a problem too if they are not accepting legitimate email. I might be a bit stubborn here but I refuse to give them the monopoly and self host our email anyway. I just wish more people would join this fight

Pretty sure this or part of this just burned me. Icing on the cake is Nintendo will also ban hammer your email if it rejects some or all of their emails - including their dumptruck of marketing junk. The only and I mean only resolution to this is to basically move your Nintendo account to a different email completely. Absolutely unreal on both sides.

Yes, no one should not have DKIM or DMARC but holy yikes when neither side wants to actually give in to help the customer.

I was viciously mean in my communication with the Outlook team when they said they “couldn’t” remove me from the blocklist. I pointed out that, as the operator of a perfectly compliant secure server their inability to deliver my mail is a technical failure on their end and one which I will be contacting their supervisor about and they somehow managed to scrabble together the heroic ability to delete my row from a table. Never back down from these bastards.

Which VPS provider out of curiosity?

Maybe don't self-host mail on a shitty $1/month VPS where 99% of the tenants are spammer scum?

This is not Microsoft's fault. The building's on fire and they're locking out the arsonists.

> Outlook.com and similar are an anathema to email. This is why they tell you not to run a mail server .

It turns out that whoever has the most power is the most powerful. This is why distributed/decentralized systems cannot singlehandedly free us from tyranny, and why I find people who spend all their time preaching decentralized systems to be quite silly. We don't need better systems (well maybe we do but,,,), we need better education and awareness of how billionaires manipulate us; this goes beyond software.

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Just put codex in a continuous goal loop to keep you off the blacklists...give it whatever email / creds it needs to make the appropriate requests and make the needed changes (ofc tell it the guardrails it should follow).

Selfhosted email is likely easier now than it ever was before.

Using self hosted email service is a big mistake in 2026.