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Office 365 Throttling Policy, Limitations & Steps to Prevent It

Published By Deepa Pandey
Anuraag Singh
Approved By Anuraag Singh
Published On September 4th, 2020
Reading Time 3 Minutes Reading
Category Office 365

When moving large amounts of email data to the cloud, the migration speed of Office 365 is often a hot topic. This is due to Microsoft Office 365 throttling policy. If you use a third-party tool to migrate to Office 365, mailbox data migration may be slow. This is a common issue when migrating to Office 365.

Microsoft is enforcing some level of message data ingestion throttling in Office 365 to protect the overall performance of the platform. This seems reasonable for shared services. However, if you only see a speed of 200MB / hour, it will slow down your email transfer a lot! Whereas, we have experienced speed up to 4GB / hour during migration to O365.

Office 365 Throttling Policy – Limitations

Microsoft uses throttling policies to limit the Office 365 resources utilized by one account. To maximize throughput and limit throttles, SysTools follows best practices and uses impersonation for best results.

An account with impersonation privileges can impersonate 100 users simultaneously and migrate 100 mailboxes in one go. The platform uses the EWS protocol. Microsoft theoretically allows for about 300MB of throughput per user per hour. SysTools platform typically provides throughput of 200-300 MB per mailbox per hour. This gives an average throughput of around 500 GB per day with 100 concurrent mailbox migrations.

If you want to further increase your bandwidth, you can create a separate migration account and create additional connectors for your platform. For example, if you create two Office 365 target connectors (each with its own separate migration account), you can migrate 200 mailboxes at the same time and achieve a throughput of approximately 1 TB per day.

Recommendations for Preventing Microsoft Office 365 Throttling

As a migration expert, SysTools has made many changes to its products to provide the best possible experience in the new world of Office 365 migration.

These practices include:

  • The key outside business hours! This may sound trivial, but during business days, the end user interacts with the system, which typically results in much higher traffic.
  • Limiting scope and settings greatly reduces the number of calls and reduces the chance of throttling. It works on only those areas of the system that need it.
  • Increasing the number of accounts connected to Office 365 does not immediately respond, try the application profile instead. When Microsoft reports these issues, it really means that the server is busy. Making more calls does not improve the situation.

These best practices should always be applied before escalation or “panic”. Microsoft offers great guidance on what happens in the event of throttling, so be sure to check it out before taking any drastic action.


The above write-up explains about Microsoft Office 365 throttling policy and the best practices to eliminate them. Throttling plays a major role while you are migrating your crucial data to Office 365. Microsoft enables throttling to provide seamless services so that users don’t face any hassle while working. Thus, you can read this article and eliminate throttling policy easily.

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