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I had a non-delivery notification from my personal mail server to outlook.com. It said "your ISP's network is on our block list.' My ISP is AWS and the network is a /14. It's bonkers.

It's like living in a 500-unit apartment complex and a company says "unit 402 didn't pay for their purchases last month, so we're not selling anything to anyone in that complex any more."

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@paco So if I'm understanding correctly, because someone on that giant subnet didn't pay now everyone is blocked?

@paco That's a common occurrence with outlook.com. At least they are deterministic and give you a chance to unblock (assuming that you own the IP address). Gmail seems to randomly reject legitimate mails, resending the exact same mail usually works then...

@WPalant I just saw this reply. But I answered it in my post. It's one EC2 instance at AWS. The IP range it comes from is a /14 range (250K IPs). I own 1 IP address from Amazon and outlook.com has no way to verify that. They did eventually get back to me after a week. They put in a mitigation. But when you're the little guy, life is hard. I only have 20 users or so.

@paco I don't think I ever had to prove that I own the IP address. Then again, if it weren't my address, I probably wouldn't bother contacting Microsoft & Co. myself. Normally they will unblock when asked without any further requirements, but it does indeed take time.

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