This is an amount of organizational resilience and user freedom that most messenger services can only dream of.
Perhaps surprisingly, I have had very little trouble with my own server; most big email providers do a good job blocking spam while permitting small independent mail servers to operate smoothly (this includs even Gmail, to my astonishment).
-There is just one exception: Microsofts Outlook.com (formerly Hotmail.com) and the other services using the same underlying infrastructure.
+There is just one exception: Microsofts Outlook.com (formerly Hotmail.com) and the other services using the same underlying infrastructure (such as live.com).
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-Over the years, except for one brief issue with AT&T, the only servers that ever rejected mails from my server are hotmail.com/outlook.com.
+Over the years, except for one brief issue with AT&T, only Microsoft ever rejected mails from my server.
This recently started happening again:
```
> do not qualify for mitigation at this time. I do apologize, but I am unable to provide any details about this situation since we do not have the liberty to discuss the nature of the block.
They did claim that "Hotmail customers have reported email from this IP as unwanted", but were unwilling to provide any details, so this is not an issue that I can diagnose.
+Instead each new response linked to a different [set of guidelines](https://postmaster.live.com/pm/postmaster.aspx) or [whitepaper](https://download.microsoft.com/download/e/3/3/e3397e7c-17a6-497d-9693-78f80be272fb/enhance_deliver.pdf).
The only explanation I have is that my mailman instance could have caused [backscatter spam](https://en.wikipedia.org/wiki/Backscatter_(email)), which I have since tried to mitigate.
They also referred me to various "programs" I could join to help manage my IPs reputation, but all of these programs require a Microsoft account.