Delivery delays for messages sent from Outlook and Exchange

Summary

Delivery delays for messages sent from Outlook and Exchange

The original impact of the issue has been mitigated by Microsoft changes. Exclaimer Engineers are continuing to work together with Microsoft to establish a root cause. If you have any questions or concerns, please reach out to our great support team, who will be more than happy to help answer any questions.

• Started

  Sep 22, 2026 · 10:58 AM

• Resolved

  Oct 9, 2026 · 8:40 AM

• Duration

  16d 21h 41m

• Severity

  None

• ◐

  Investigating

  Sep 22 · 10:58 AM Exclaimer

  Exclaimer engineers are investigating a delivery delay affecting some messages sent from Outlook and Exchange to Exclaimer Cloud. Some of these messages may be retried by the sender and may appear as temporary deferrals rather than delivery failures. We are not currently aware of any confirmed message loss and will provide updates as we learn more.

• ◆

  Identified

  Sep 22 · 3:19 PM Exclaimer

  Exclaimer has identified that a small subset of messages (~0.02%) are delayed when routed through Exclaimer due to a suspected issue within Microsoft's servers. This has been raised with Microsoft to investigate alongside Exclaimer Engineers. Sent messages will be received with a signature applied, as expected. If you are seeing issues with message deliverability, please reach out to our support team, who will be happy to assist.

• ◉

  Monitoring

  Sep 27 · 7:33 PM Exclaimer

  Mail delivery has resumed as normal and our engineers are seeing significantly less errors. The team are awaiting confirmation of a fix implemented on Microsoft servers and will be monitoring until tomorrow morning to confirm.

• ✓

  Resolved

  Oct 9 · 8:40 AM Exclaimer

  The original impact of the issue has been mitigated by Microsoft changes. Exclaimer Engineers are continuing to work together with Microsoft to establish a root cause. If you have any questions or concerns, please reach out to our great support team, who will be more than happy to help answer any questions.