This happens every 3 months now:
2023-10-29T19:22:20.569+00:00 1qxBMV-0086ua-AC ** <redacted>@hotmail.com
P=<redacted> R=dnslookup_ipv4 T=remote_smtp
H=hotmail-com.olc.protection.outlook.com [104.47.58.161]:25
I=[209.16.157.42]:40134
X=TLS1.2:ECDHE_SECP384R1__RSA_SHA256__AES_256_GCM:256 CV=yes
DN="C=US,ST=Washington,L=Redmond,O=Microsoft
Corporation,CN=mail.protection.outlook.com":
SMTP error from remote mail server after MAIL FROM:<redacted> SIZE=4773:
550 5.7.1 Unfortunately, messages from [209.16.157.42] 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.
[BN8NAM11FT042.eop-nam11.prod.protection.outlook.com 2023-10-29T19:22:20.489Z
08DBD7DEDE23957D]
Every time I go through the mitigation dance and then it just happens
again 3 months later. They've been doing this for over 2 years now.
Between the last mitigation on 2023-08-16 and now there have been a
total of 3 emails delivered to Hotmail.
In the same period two other outgoing IPs have sent 9 and 8 emails to
Hotmail but they have never experienced a single S3150 rejection.
I know from netflow data that there's barely any SMTP traffic to Hotmail
in the entire network (and only certain IPs are authorised to make SMTP
connections) so why does Microsoft keep blocking me repeatedly?
(SNDS: "All of the specified IPs have normal status")
--
Simon Arlott
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