Possible Routing issues within MEA & US region for Microsoft Customers

Update timeline

1. investigating Apr 04, 2026, 10:00 AM UTC

   Exclaimer Engineers are investigating a possible issue for customers in the MEA region who are unable to route emails to Exclaimer for Server-Side signatures, with messages being deferred and delayed. Emails are continuing to be processed. If any possible sending delay needs to be avoided, you can disable the Mail flow rules for Exclaimer Cloud within the Exchange Admin Center. This does not look to impact all customers within the region. More information will be provided when available.

2. identified Apr 04, 2026, 02:44 PM UTC

   Exclaimer Engineers are continuing to investigate issues affecting customers in the MEA region who are facing delays or deferrals when sending emails. Our findings indicate that Exclaimer itself is functioning properly in the region, and successful connections are being established for all incoming messages. Occasionally, we notice that our monitoring systems initiate a connection but then disconnect before completing the message transfer. Since these cases don't reach our servers, it suggests that the problem is likely outside of Exclaimer's framework, occurring when the sending email server attempts to route messages. We have contacted Microsoft to further investigate the situation. For customers experiencing delays in mail flow, an immediate workaround is to disable the Exchange Mail Flow rules. Despite the delays, we confirm that all messages are eventually being processed by Exclaimer as expected.

3. identified Apr 06, 2026, 01:44 AM UTC

   We are seeing continued improvements in mail flow performance. We are currently working with Microsoft to confirm whether their fix has been fully deployed. Error rates have decreased, and we are no longer observing issues in the MEA region. However, some customers in the US region are still experiencing impact. At this time, the mail flow rule disablement workaround can be safely reverted for customers who previously applied it to avoid delays. For customers who are still experiencing the issue, or encounter any new occurrences, we recommend disabling the Exclaimer transport rule (mail flow rule) as a temporary workaround. We will continue monitoring the situation closely and will provide further updates once we receive confirmation from Microsoft.

4. identified Apr 06, 2026, 01:45 AM UTC

   We are continuing to work on a fix for this issue.

5. identified Apr 07, 2026, 01:18 AM UTC

   Error rates have continued to decrease, and we’re now seeing minimal errors across both the MEA and US regions. We’re still actively working with Microsoft to better understand the root cause, overall impact, and confirmation of the fix. If the issue continues for any affected users, disabling the Exclaimer transport (mail flow) rule remains a valid temporary workaround.

6. monitoring Apr 08, 2026, 10:43 AM UTC

   Exclaimer Engineers are continuing to monitor the situation at this time. The rate of messages being deferred due to the connecting server failing to provide the email has dropped substantially as well since Monday. We are continuing to reach out to Microsoft to discuss the issue and obtain a complete understanding of it, and to confirm that the issue has been addressed.

7. resolved Apr 16, 2026, 06:57 PM UTC

   After extended monitoring, we are no longer seeing any issues impacting customers within these regions that would cause the issue initially reported at this time. We continue to reach out and discuss the incident with Microsoft, and will provide a Postmortem review once we have received completed feedback from them regarding this issue.

8. postmortem Apr 20, 2026, 06:14 PM UTC

   Issue: Possible Routing issues within MEA & US region for Microsoft Customers Incident Length: ~70 hour\(s\) Incident Date: 4/4/2026, UTC 9:37– 8:07 7/4/2026 Incident Status: Investigating **Summary** Mail flow for customers in the Middle East and Africa \(MEA\) region would encounter issues routing messages to Exclaimer, with Exchange servers reporting that the exclaimer smtp hosts rejected or did not respond to the request. We are still awaiting a full Post Incident Review from Microsoft and will update this Postmortem with additional information once it is available. **Root Cause** The issue is believed to be a configuration issue within Exchange in the region, preventing the connection to Exclaimer servers within the UAE or US region. All impacted messages appear to have been deferred, resulting in them being delivered at a later time, further confirming the expected mail flow between Exclaimer and Exchange Online. **Mitigation** Some Exchange servers which were consistently noted to be failing to provide the email to Exclaimer relays when requested, were passed over to Microsoft for review. Shortly afterwards these instances stopped appearing to submit traffic to Exclaimer, suggesting they have been had been taken out of service. Exclaimer Engineers have internally made changes to how message logs are stored between our servers, helping to improve and identify potential issues and errors within the STARTTLS process