On sunday I got some bounces because someone (wasn't his fault, of course) tried to register at my hub using an outlook.com-address:
said: 550 5.7.1 Unfortunately, messages from [188.8.131.52] weren't sent.
Please contact your Internet service provider since part of their network
is on our block list (S3150). You can also refer your provider to
[HE1EUR01FT024.eop-EUR01.prod.protection.outlook.com] (in reply to MAIL
Well, I can't do a thing about this - everything is set up alright (SPF, reverse/forwad lookup) and according to the messege Microsoft elected to ban a whole IP range - the (V4) rrange my server is in. There's precisely nothing I can do about this (btw, why has outlook.com no V6 addresses?). If I remember correctly, Microsoft completely ignores requests: Even if one of your customers is guilty of spamming and you remedy the situation, you're still banned - no matter what you do. So contacting Microsoft (which I would be the wrong person, anyway, it would have to be Netcup) is a waste of time. So I changed the registration text to include a warning not to use outlook.com-addresses.