Exclaimer Add-in: [domain] is not an Exclaimer Customer

Update timeline

1. investigating Mar 03, 2025, 05:13 PM UTC

   Customers using the Exclaimer Outlook Add-in may experience an error: "[domain] is not an Exclaimer Customer". Engineers from Exclaimer and Microsoft are currently working to resolve this issue and we will provide updates as we know more. We appreciate your patience in the meantime.

2. monitoring Mar 04, 2025, 10:31 AM UTC

   Our Engineering team has been monitoring the system's error rate since a significant drop in the number of failures was recorded at 18:50 GMT on March 3rd. We are continuing to monitor in the event the error rate increases again and maintain communication with Microsoft as well.

3. resolved Mar 05, 2025, 10:14 AM UTC

   Engineers from Microsoft have been able to identify the root cause of the issue and implement a permanent fix. Exclaimer has continued to monitor the event for any additional reports and can confidently confirm there are no further instances of the error at this time. Additional information will be provided once the RCA from Microsoft has been completed. If you are experiencing issues with your signatures, please contact our support team for more assistance.

4. postmortem Mar 12, 2025, 08:11 PM UTC

   Issue: Exclaimer Add-in for Outlook returned the error message ‘domain’ is not an Exclaimer Customer and did not provide Client-side signatures. Incident Length: 7 hours and 20 minutes Incident Date: 03/03/2025, UTC 11:40 – 19:00 Incident Status: Resolved **Summary** Customers within the US may have experienced an issue where the Exclaimer Add-in would report that their domain was not a valid customer of Exclaimer, preventing any client-side signature from being applied whilst composing emails. There was no impact to server-side signature application during the time. **Root Cause** A Point of Presence \(POP\) machine used as part of Exclaimer’s Content Delivery Network within Microsoft Azure infrastructure within the US failed to correctly handle requests, returning a HTTP 404 response to some requests made within the US region. After contacting Microsoft, they were able to identify the impacted machine and resolve the issue with its routing. **Mitigation** Due to the timing of the incident, an update to the Exclaimer Cloud Add-in had been released earlier in the day, resulting in a rollback of the update being performed to rule out correlation to the update and the issue being experienced by customers. Once the fault had been identified as located within the content delivery network within the US, an urgent request was raised with Microsoft to investigate the issue. Once the POP machine that was experiencing an issue with the rule sets was repaired and confirmed to be functioning correctly, errors advising ‘is not an Exclaimer Customer’ reduced dramatically to expected levels. **Incident Timeline** 12:53 – Customer reports of ‘Domain is not a customer’ were received by Support personnel, initial troubleshooting began to investigate individual causes. 13:30 – Increased number of reports suggested a large issue occurring relating to the Add-in. Exclaimer Engineers were contacted to investigate. 13:57 An incident was raised internally to investigate the cause of the error due to a large, continued level of reports from customers 14:01 – Exclaimer Engineers identified start time of initial increase of the error. 14:08 – The error was determined to primarily impact US region customers. Additional engineers were contacted to review for any ongoing issues within the US region. 14:31 – Exclaimer Engineers verified that no configuration changes had taken place within the US region. 15:39 – Roll back of the Exclaimer Add-in was performed to verify that no changes within the Add-in caused the issue being seen. 16:00 – Rollback of the Add-in was completed by Engineers, but the error rate was unchanged. 16:10 – Engineering verified around 3% of domains were failing to return a result. 16:16 – A review of Content Delivery Network was completed and confirmed there was no issue with the data stored within, requests for data through the CDN were also successful. 16:55 – A high priority case was raised with Microsoft to investigate for possible issues. 19:00 – Exclaimer Engineers confirmed that the error rate had substantially dropped within our monitoring. 04/03 08:51 – Following a Microsoft internal investigation, Microsoft advised that requests from a specific POP located within the US were being incorrectly routed, resulting in the requests failing to find the CDN as expected. 10:15 – Monitoring of the service continued until Microsoft confirmed full resolution of the POP system 13:35 – Exclaimer Add-in version 1.23.200 was redeployed after confirming that the issue was resolved.