Symptom

A Microsoft 365 backup fails with the following error:

This can happen for Exchange, OneDrive, SharePoint or Teams.

Cause

The third-party provider referred to in the error message is Microsoft. 

To enable us to backup and restore M365 data, we make use of the Microsoft Graph API. Microsoft limits the number of concurrent calls our system can make to this API within a certain time period, as well as the number of files that can be accessed. These limits ensure the stable performance of Microsoft's services, but they also have implications for backups.

If our service exceeds the allowed limit of calls within a given time period, any further calls made within the same period are throttled (cut off) by Microsoft. Throttling often occurs during popular backup times, when M365 backups for many customers are running in our system simultaneously. Backups that were in progress when throttling occurred will only resume once the specific time period elapses. 

Solution

Throttling is controlled by Microsoft and as such cannot be resolved by our support team. Below are steps you can take to prevent throttling errors.

1. Wait for the next scheduled backup, which is likely to be successful.

2. Wait at least 30 minutes after seeing the error, then manually initiate a new backup.

3. Permanently reschedule the backups for the affected backup set/s to a different time.

4. Consider what other apps in your environment could be running against the Microsoft API, as Microsoft's limits are shared across all apps for your tenant.

5. Check your backup selection for the presence of nested folders, which can slow backups down. Reconfigure the data structure if necessary.

6. Check your backup selection for the presence of large files (>300MB). These can slow backups down and should not be protected as part of OneDrive or SharePoint. Consider a file server instead.

7. You may want to disable applications such as Microsoft Power Automate which frequently add files or make updates to the data in the backup selection.