How to increase EWS throttling limits, when migrating to Office 365 (Exchange Online).
You cannot disable throttling in Office 365. However, if you have at least 1,000 seats, you can make a request to Microsoft Support to have your EWS throttling limits increased for up to 60 days.
You should only request this when the following are true:
If both of the above are true, contact Microsoft and ask to have the following EWS throttling limits raised for 60 days. Note: These values have been approved by Microsoft.
Note: Public Folders do not use impersonation, but the migration could benefit from raising the EWS limits.