I have fought this battle before, and in my case it turned out to be a
compromised user account. Check logs for a sender with unusually high
volume. While you're waiting for the response to your ticket you can
use your time to hunt for that underlying problem. I do wish they
provided samples of the offender's messages, as that would remove any
doubt and make it much easier to see where the problem is.
They also may not unblock you for some period of time after the activity
stops. I have had it take days.
------ Original Message ------
From: "Rauf Guliyev via mailop" <mailop@mailop.org>
To: mailop@mailop.org
Sent: 9/9/2020 5:58:52 PM
Subject: [mailop] Anybody seeing a huge spike of (S3140) errors from
Hotmail/Outlook started on Sep 7th
Hello there,
We are seeing a huge spike in "550 5.7.1 Unfortunately, messages from
[IP.AD.DR.ES] weren't sent. Please contact your Internet service
provider since part of their network is on our block list (S3140)"
errors while sending to Hotmail/Outlook. It started on Sep 7th and is
affecting only one datacenter, the rest is sending the same emails
just fine. The SNDS shows the affected IPs as green. Filed a ticket
(SR1508383241) but curious to see if it's widespread.
Thanks in advance,
Rauf
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