Bounce message sample:
From: Mail Delivery Subsystem <MAILER-DAEMON@outbound1.exchangedefender.com>
Sent: Tuesday, July 28, 2026 1:17 PM
To: xxxxxx@msn.com <xxxxxx@msn.com>
Subject: xxxxxxx
----- The following addresses had permanent fatal errors -----
<xxxxxxxx@msn.com>
(reason: 550 5.7.1 Unfortunately, messages from [207.210.228.195] weren't sent. Please contact your Internet ...DD0E557A63D1E] [BL6PEPF0001AB4E.namprd04.prod.outlook.com 08DEE872B1014535])
----- Transcript of session follows -----
... while talking to msn-com.olc.protection.outlook.com.:
>>> MAIL From:<xxxxxx> SIZE=3621867
<<< 550 5.7.1 Unfortunately, messages from [207.210.228.195] 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. [Name=Protocol Filter Agent][AGT=PFA]
554 5.0.0 Service unavailable
Update 07/29/2026 19:52 PM 2 hrs
We have received reports of ExchangeDefender IP addresses listed on Microsoft's freemail services.
We have raised an issue with Microsoft SNDS and we are awaiting delisting. In the meantime, IP addresses have been removed from outbound rotation so any RBL rejections but some rejections are still coming in as if cached. We have not received any reports of abuse nor are we able to escalate the issue.
In the meantime, and if you urgently need to deliver mail from your email address to msn.com or live.com, you can rely on our bypass.exchangedefender.com service that its included with your license. Just login to admin as usual, click on Bypass and then send email bypassing the ExchangeDefender network entirely.