Am 14. August 2019 um 20:44 Uhr -0000 schrieb brian@emwd.com:
Did you keep an eye on the reputation on the IP addresses you were sending from? Sometimes an IP address just doesn't send enough volume of mail to build one up.
This mail server ever only sent my personal and my family's e-mail -- no public mailing lists. The volume was very low. Maybe about ten e-mails a week in average, sometimes no e-mail a week at all. If low e-mail volume is indeed a criterion, then it could be the cause. But low volume as a spam criterion strikes me as doubtful, because a spammer specifically wants to issue mass e-mail.
The server was online since I think 2013 and always had the same IP. It wasn't a shared IP, i.e. this mail server was the only one sending from that IP. The spam classification problem was there from the very beginning.
We did get that fixed. The key to Microsoft is to sign up for their Hotmail Feedback Loop. They also provide a nice interface (SNDS) that shows you what they think of your IP addresses so you can mitigate any potential delivery issues ahead of time.
I'm leaving that to my SMTP relay provider now. I find it too much hassle to sign up for such services just for my private e-mail. I'm not getting paid for sinking my time into this; keeping the server running and clean is enough of time investment into my hobby (I use it for other things than e-mail, too). Microsoft is not the only e-mail provider, so if all e-mail providers did it like that, you'd have to create dozens and hundreds of accounts. Microsoft's pure size is what allows them to pose such a restriction successfully. The real problem is the centralisation of services at only a few providers.
Yahoo is the worst.
Luckily, Yahoo e-mail addresses are so rare in Germany that I can ignore them. I don't have anyone with a Yahoo address in my address book currently. outlook.com is much more common, but from my experience most German e-mail addresses are hosted by the United Internet group (GMX et al.), which I never had problems delivering to. They do a decent job. As for GMail, after a few attempts with followup questions my contacts started looking into their spam folder. That's why I was fine without the SMTP relay provider for years. But since recently, more and more people use outlook.com, which outright rejected.
The majority reason why messages ends up in Spam folders has nothing to do with the mail server at all. It is because the content of the message comes across as spammy, i.e. a message that contains several URLs, using exclamation points, etc.
Normal private 1-1 correspondence usually does not fulfill these criteria, and I've still been filed/rejected as spam (and likewise other family members). I felt like Don Quixote fighting the windmills. Today's e-mail infrastructure makes things difficult for private individuals who want to self-host.
Anyway, I think this subthread has grown large enough. My questions were answered. Thanks to everybody who commented!
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