Application Impersonation retired by Microsoft 365 - Action is required if you still use Exchange Web Services

If you have a service account connection through Microsoft 365 and have not completed the migration from Exchange Web Services (EWS) to Graph API then we will soon no longer be able to sync your calendars, and this may already be the case. Follow our guide to complete the migration as soon as possible, https://docs.cronofy.com/calendar-admins/faqs/ews-migration/

From 07:20 UTC today, we saw an increase in errors when performing EWS sync operations with Microsoft 365. The initial increase in errors tailed off as we stopped attempting to perform syncs which were no longer allowed.

At 13:20 we began sending additional emails out to customers who have yet to complete the migration from EWS to Graph API.

Again, we urge any customers who have not completed the migration from EWS to Graph API to do so as soon as possible.

We are continuing to monitor the situation. We are also sending additional emails to those who have yet to complete the migration from EWS to Graph API.

We are continuing to monitor the situation and have no further updates at this time

We strongly believe the errors we are seeing are related to ApplicationImpersonation being retired by Microsoft 365.

For more information and to restore connections please follow the instructions on our docs site - https://docs.cronofy.com/calendar-admins/faqs/ews-migration/

We are continuing to monitor. The errors our telemetry shows are very gradually reducing.

We will reduce the frequency of updates as we continue to monitor.

We are continuing to monitor for any further issues.

Metrics continue to trend in the right direction but we're still seeing a very small number of errors being returned from Microsoft 365.
We are continuing to monitor.

The number of EWS sync operation errors with Microsoft 365 continues to decrease, but they are not quite back to usual levels. We are continuing to monitor.

Our telemetry shows that the number of errors is decreasing but have not returned to normal levels, and that Microsoft Graph API syncs are operating as normal, this is only impacting EWS sync operations.

Other background processing tasks are not impacted by this incident.

We have identified an issue with calendar sync operations when connecting to Microsoft 365. We are seeing a higher error rate than usual, but most sync operations are still successful.