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Split from this thread.
This issue has become a headache for one of my clients with one user alone receiving in excess of 20,000 NDR's over the weekend.
As you can see I have NDR Backscatter ON and also blocked the Sender email in the Spam filter blocked sender list.
Client still receiving NDR's
There are 6 users for this one particular client and the 'From IP' addresses in the properties of the messages are:
10.168.54.145
10.169.245.12
10.141.47.152
10.165.234.158
10.163.6.145
10.165.244.142
I have no Idea where the above IP's come from!!
Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
Locked Question. This question was migrated from the Microsoft Support Community. You can vote on whether it's helpful, but you can't add comments or replies or follow the question.
Answer accepted by question author
Hi RonaldGray_66,
Thanks for the information.
I have analyzed the NDR and found it is the same as the original one. Our engineer is working on it, please keep monitoring the main thread. Once the issue is resolved, we will share the solution there.
Regards,
Robert
Hi RonaldGray_66,
This is an backscatter related issue. Our engineer is working it, please keep monitor the main thread. Once the issue is resolved, we will share the solution in there.
Meanwhile, please try the following two workarounds:
1.Setup backscatter = enable, based on customer's feedback, sometimes, it doesn't work.
For Office 365 users, in Exchange admin center > protection > spam filter > edit the spam policy >advanced options, set the NDR backscatter to on. After that, these backscatter emails will be marked as spam.
2.You can create a shared mailbox and a corresponding transport rule to redirect all NDRs to this shared mailbox. Then, you can check all NDRs in the shared mailbox regularly.
Update: To identify whether you are in the same situation, please send us the complete NDR error message for analysis.
To protect the privacy, I have sent you a private message to collect the information. Click the following link to access it:
https://answers.microsoft.com/en-us/privatemessages/list
Regards,
Yang
Guys, this is getting ridiculous. I have clients who have received over 20,000 NDR's over the weekend.
What are you doing to fix this?