Microsoft's mail blocking is very aggressive.
I've dealt with this a few times. Each time we found a compromised
email account on our system. So if you haven't already done so, I'd
analyze logs looking for an unusually busy sender.
The catch is that after you fix whatever the problem is you'll still be
blocked for several days afterwards. I do wish they'd provide samples
of whatever messages set off the blocking. In a perfect world I'd also
want a way to send them an "all clear" that the problem is resolved.
-- Original Message --
From: "Andy Smith via mailop"
To: mailop@mailop.org
Sent: 9/8/2020 6:15:16 PM
Subject: [mailop] What's Microsoft's S3150 block list and where do I go
to request removal?
Hi,
We have a customer who's been receiving Icinga (basically Nagios)
alerts every few hours for the last few days to their hotmail
address. The customer could/should have either addressed the
situation or halted the alerts, but they didn't and that's their
choice.
In the third day of this we've started getting this NDR:
[removed]@hotmail.com
host hotmail-com.olc.protection.outlook.com [104.47.55.161]
SMTP error from remote mail server after pipelined MAIL
FROM: SIZE=2107:
550 5.7.1 Unfortunately, messages from [85.119.80.238] 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
http://mail.live.com/mail/troubleshooting.aspx#errors.
[BN8NAM12FT030.eop-nam12.prod.protection.outlook.com]
So, what's "S3150"? — it isn't mentioned at all on
http://mail.live.com/mail/troubleshooting.aspx#errors — and where
should I be going to request delist?
I realise I need to sort out SPF for that envelope sender.
All of the mails will have been almost identical so I can see why
something might have been triggered, however they were requested by
the recipient.
Cheers,
Andy
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