How to: Transfer large amount of data to/from Microsoft 365 Exchange Online
In case you need to backup or restore large amount of Microsoft 365 Exchange Online data, it can be beneficial to enable Diagnosis mode to be able to transfer even more data before being throttled. This is a good way to ensure a faster first backup, or a large restore.
Access your Microsoft 365 admin center and click the question mark in the top right corner.
Enter EWS in the search field and click the text link Increase EWS Throttling Policy
Click the Run test button to start the process.
When it’s loaded you can choose a number of days where the throttle limit is disabled. Then click Update settings
And you’re done. Now more data can be transferred, without it being throttled as much as before.