Some users' outbound Exchange Online email messages may be marked as spam and not delivered

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 continuing the process of identifying the IP addresses that are causing the third-party anti-spam service to activate and block a segment of Microsoft’s email IP address ranges. While we are seeing signs of improvements to some IP address ranges that we've identified thus far, we'll share an updated timeline for this investigation and the steps being taken to remediate the impact when more information is available.

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: Wednesday, April 3, 2024, at 11:00 PM UTC

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 continuing to isolate the IP addresses that are responsible for triggering the third-party anti-spam service and blocking a portion of Microsoft's email IP address ranges. We'll provide an updated timeline for this process and the remediation of impact once it becomes available.

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: Wednesday, March 27, 2024, at 11:00 PM UTC

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 continuing our operation to identify and isolate IP addresses which are responsible for triggering the third-party anti-spam service to block a portion of Microsoft's email IP address range, although more time is needed for this to complete. Once complete, we'll work towards mitigation by limiting the mail flow from these IP addresses.

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: Monday, March 25, 2024, at 11:30 PM UTC

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: Our operation to isolate the IP addresses that are causing the third-party anti-spam service to block a portion of Microsoft’s email IP address ranges is taking longer than expected. After this is complete we'll proceed with limiting the mail flow to prevent the issue from reoccurring.

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 22, 2024, at 11:30 PM UTC

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 continuing the previously mentioned operation to isolate the IP addresses that are causing the third-party anti-spam service to block a portion of Microsoft’s email IP address ranges, after which we'll proceed with limiting the mail flow to prevent the issue from reoccurring.

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: Thursday, March 21, 2024, at 11:30 PM UTC

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: Our mitigation efforts are underway as we continue to work with the third-party anti-spam service to monitor the relevant IP ranges and isolate which IP addresses may be responsible for the malicious email messages causing the service to block Microsoft IP ranges. We'll be able to limit the mail flow from these once identified, which should serve as a long-term solution for this issue.

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: Wednesday, March 20, 2024, at 11:30 PM UTC

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 continuing our efforts of working with the third-party anti-spam service to monitor the IP address ranges affected by this problem and identify which IP addresses may be causing the mass delivery of malicious email messages. Once we've isolated the IP addresses that are causing the third-party anti-spam service to block a portion of Microsoft’s email IP address ranges, we'll limit the mail flow as a long-term solution to prevent the issue from reoccurring.

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: Tuesday, March 19, 2024, at 11:00 PM UTC

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 continuing to work with the third-party anti-spam service to monitor the IP address ranges affected by this problem and identify which may be sources of potentially malicious email messages so we can determine our next troubleshooting steps for reducing such email messages and the frequency of those IP addresses being blocked. In parallel, we're continuing to assess potential long-term solutions to address this and similar problems in the future.

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: Tuesday, March 12, 2024, at 11:00 PM UTC

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

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 continuing to conduct rule optimizations in our efforts to minimize the outbound spam and as we manually unblock affected IP addresses to help reduce the impacted mail flow. Due to the nature of these potential harmful email messages we may not be able to unblock certain IP address right away until they have been fully vetted.

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: Wednesday, March 6, 2024, at 9:00 PM UTC

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've determined that a third-party anti-spam service is blocking a portion of Microsoft's email IP address ranges after a higher-than-normal amount of potential harmful email messages were being sent by organizations that leverage the Exchange Online service. We're conducting rule optimizations in our efforts to minimize the outbound spam and as we manually unblock affected IP addresses to help reduce the impacted mail flow.

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 1, 2024, at 8:00 PM UTC

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 continuing to review the affected IPs and their relationship with a third-party email protection service to better understand the impacting behavior and formulate a remediation plan. Additionally, we're working to identify ways to reduce the outbound spam to help prevent future occurrences of this issue.

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: Thursday, February 29, 2024, at 8:00 PM UTC

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: The process of reviewing the affected IPs and their relationship with a third-party email protection service to better understand the impacting behavior and formulate a remediation plan is ongoing. We're aiming to have a more substantive insights to share by our next scheduled update.

Scope of impact: Your organization is impacted by this event, and the problem impacts all users sending outbound email messages.

Next update by: Tuesday, February 27, 2024, at 8:00 PM UTC

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 continuing to review the affected IPs and their relationship with a third-party email protection service to further our understanding of the impacting scenario and determine our next 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 10:00 PM UTC

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: Our investigation is progressing, though our review of service side logs as well as affected IPs which may be related to the cause of impact, is taking an extended period of time. We'll provide an update on the status of the investigation, including our findings if pertinent, by our next scheduled update.

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 8:00 PM UTC

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

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.