[German]Microsoft has a problem with its Exchange Online instances that can easily sideline its customers. The sender domains for emails are classified as spam and rejected. This means that companies can no longer send mail. After I discussed this several times here in the blog, a blog reader sent me confirmation from Microsoft.
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Microsoft 365: Mails are rejected as SPAM
It is an issue that drives administrators of Microsoft 365/Exchange online instances to despair. The emails sent are rejected by the recipient as SPAM. I first reported in the blog post Microsoft IP addresses landed on blacklists (Jan. 2023) that Exchange Online users are running into problems with mail delivery because IP addresses held by Microsoft end up on blacklists.
For the reader's customers, it affected the IP address 40.107.20.44. This was rectified, but the next case hit me in mid-February 2024. I wrote about this within my German blog: More German customers, also government organizations has been hit. There has been a thread Emails being blocked by Gmail from office 365 in the Microsoft Answers forum since March 3, 2023 about Emails being blocked by Gmail from office 365, which deals with the same phenomenon. The thread already has many pages, so it's a bigger problem that has probably never been addressed.
Microsoft confirms SPAM issue
A German blog reader points out in this comment that the message has been displayed in the Azure admin portal "for some time" that some users' outgoing Exchange Online email messages may be marked as spam and not delivered. This has been going on since February 26, 2024 and continues.
German blog reader Andreas P. has now sent me some status excerpts from the Azure and Microsoft 365 admin portal, which show me that Microsoft is now aware of the problem. The first full-text message in the status area appears to be from February 26, 2024. Here is the text.
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Published Time: 26.02.2024 05:51:48
Title: Some users' outbound Exchange Online email messages may be marked as spam and not delivered
User impact: Users' outbound Exchange Online email messages may be marked as spam and not delivered.
More info: This isn't connection method specific and thus occurs in all Exchange Online connection methods. Affected users receive a Non-Delivery Report (NDR) message that references the third-party anti-spam service name that has added the IP address to their block list.
Current status: We're currently investigating service side logs as well as affected IPs provided by some reporting users to pinpoint the cause of impact and cultivate our troubleshooting steps.
Scope of impact: The problem may impact some users sending outbound email messages if they're leveraging a specific third-party anti-spam service mentioned within the NDR.
Next update by: Monday, February 26, 2024, at 6:30 AM UTC
Published Time: 26.02.2024 05:35:13
Title: Some users' outbound Exchange Online email messages may be marked as spam and not delivered
User impact: Users' outbound Exchange Online email messages may be marked as spam and not delivered.
Current status: We're investigating a potential issue and checking for impact to your organization. We'll provide an update within 30 minutes.
These status updates are published at cyclical intervals. I have the full text of the last status update dated March 6, 2024. It contains the following information:
Published Time: 06.03.2024 21:48:27
Title: Some users' outbound Exchange Online email messages may be marked as spam and not delivered
User impact: Users' outbound Exchange Online email messages may be marked as spam and not delivered.
More info: This isn't connection method specific and thus occurs in all Exchange Online connection methods. Affected users receive a Non-Delivery Report (NDR) message that references the third-party anti-spam service name that has added the IP address to their block list.
Current status: We're working with the third-party anti-spam service to better identify the IP
address ranges affected by this problem, so that we can more quickly identify and manage sources of potentially malicious email messages. This will help reduce the frequency of spam and phishing email, which would also reduce the number of reported and blocked IP addresses, returning some mail flow as expected. In parallel, we're reviewing long-term solutions to prevent similar problems.
Scope of impact: The problem may impact some users sending outbound email messages if they're leveraging a specific third-party anti-spam service mentioned within the NDR.
Root cause: A third-party anti-spam service is blocking a portion of Microsoft's email IP address ranges to protect organizations that use their services.
Next update by: Friday, March 8, 2024, at 9:00 PM UTC
According to Microsoft, this problem is not connection method-specific and therefore occurs with all Exchange Online connection methods. This means that experimenting with DKIM entries etc. generally does not help much. Affected users will continue to receive an NDR (Non-Delivery Report) message that refers to the name of a third-party anti-spam service that has added the IP address to its block list.
Currently, Microsoft has no choice but to work with the third-party anti-spam service to better identify the affected IP address ranges and get them off the block lists.
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