Server side emails bouncing - Error message - Need Mail Command

Update timeline

1. investigating Apr 01, 2026, 05:26 AM UTC

   We are investigating issues with emails failing to route through Exclaimer for server side signature imprints. For now, we recommend disabling server side transport rules in Exchange Online (Identify messages to send to Exclaimer cloud) to ensure mail flow. We will continue to update as more information becomes available.

2. monitoring Apr 01, 2026, 07:25 AM UTC

   We have identified that the issue was caused by an internal mail‑processing component that had recently been enabled. Under certain conditions, this component could interfere with message handling and lead to the errors observed. The feature has now been disabled, and the issue has stopped. An unrelated third party was incorrectly attributed to the issue earlier. We have identified other internal changes that coincided with the timing of the incident, and these have been rolled back as a precaution. We are continuing to investigate to ensure there is no further impact. The service has remained stable since our last update, and we are continuing to monitor closely.

3. resolved Apr 01, 2026, 02:17 PM UTC

   After continued monitoring, we have confirmed that emails are now being processed as expected through Exclaimer. If you disabled the Exclaimer Mail Flow rule, please look to enable this again when ready. If you are continuing ot see issues, please reach out to our support team, who will be happy to help.

4. postmortem Apr 09, 2026, 07:42 PM UTC

   Issue: Messages failed to be routed through Exclaimer correctly within AU region Incident Length: 3 hour\(s\) and 6 minutes Incident Date: 01/04/2026 UTC 05:53– 8:59 Incident Status: Resolved **Summary** Australian Region customers with the Sent Items feature enabled would encounter an issue routing messages, resulting in message delivery issues and non-delivery reports \(NDRs\) being received. **Root Cause** The issue was caused by a recently enabled mail processing feature globally, which introduced unexpected behavior within the SMTP proxy servers. This affected how messages were handled when routing back to Exchange Online. **Mitigation** Initial resolution was implemented by reverting the mail processing feature update globally. Further improvements to error handling have since been implemented to identify the cause of similar issues faster in the future. **Incident Timeline** 01/04 5:53 – Incident is declared after customer reports of mail flow issues are received to the Support Team 5:57 – Initial investigation indicates the issue appears to be isolated to AU region customers. 6:03 – Exclaimer Engineers confirm the resulting error code correlates with error logs within internal logging 6:32 – Initial hypothesis suggests degradation with an external SMTP provider is the cause of the issue. Whilst they announce a fix, the backlog of impacted messages does not change. 6:41 – Error rates begin to decrease and incident is believe to be resolved. 7:08 – Exclaimer Engineers monitoring note that a drop in 5xx errors is visible, along with a drop in active message counts. Suggesting correlation between the errors being seen and the number of messages submitted to Exclaimer. 7:32 – Engineers begin investigating internal systems further for any lingering issues. 7:37 – The error is confirmed to be related to routing the email back to Exchange Online, disproving the earlier hypothesis. Recent changes to mail routing are reverted to monitor for impact or changes. The error rate is noted to instantly drop at this time. 8:03 – The error rate begins to approach zero, investigation into the cause within recent releases begins. As part of this incident, areas of improvement within internal and external communication have been identified. Action has been taken to improve this and prevent future instances of misattribution and miscommunication from occurring.