How to Increase or Disable EWS Throttling in Exchange Online
Exchange Online applies throttling limits to maintain service availability and balance resource usage across Microsoft 365 environments. During large mailbox migrations, these limits can affect the number of requests a migration application can process at a given time and may increase the overall migration duration.
Administrators planning large Exchange Online migration projects can review EWS throttling settings to understand how these limits influence migration performance. Adjusting throttling settings may help optimize certain migration scenarios when required and configured according to the organization's migration requirements.
EdbMails supports secure Office 365 migration with features designed to help administrators manage large-scale mailbox transfers efficiently while maintaining control over the migration process.
What Is EWS Throttling in Exchange Online?
Exchange Web Services (EWS) throttling is a Microsoft 365 service protection mechanism that controls how applications access Exchange Online resources. Microsoft applies throttling limits to ensure that a single application or workload does not consume excessive resources and affect the availability of the service for other users.
During Exchange Online migration, migration applications use Exchange Web Services APIs to access mailbox data and transfer it between environments. When the number of requests exceeds the allowed limits, Exchange Online may temporarily reduce request processing speed by applying throttling, which can affect migration throughput and increase the time required to complete large mailbox transfers.
EWS throttling does not indicate a migration failure. Instead, it is a resource management feature designed by Microsoft to maintain service stability. Administrators can review throttling behavior and adjust migration planning, batch sizes, and configuration settings when required to achieve better migration performance.
How to Prevent EWS Throttling in Office 365
EWS throttling is controlled by Exchange Online to maintain service stability, but administrators can take several steps to reduce its impact during migration. Proper workload planning, migration scheduling, and monitoring can help maintain better migration performance.
Before starting a large Exchange Online migration, consider the following practices:
- Plan migration batches carefully: Avoid starting too many migration batches at the same time. Maintain sufficient intervals between multiple migration batches to help manage Exchange Online resource usage.
- Avoid heavy concurrent activities: Running other resource-intensive tasks along with mailbox migration can increase the load on Exchange Online. Avoid scheduling heavy mailbox operations or other large-scale activities during the migration process.
- Manage requests to the same mailbox: Exchange Online may apply throttling when applications generate a high number of requests to the same mailbox or service resources. Managing migration workloads appropriately can help reduce unnecessary throttling responses.
- Reduce unnecessary mailbox activities: Minimize additional mailbox processing activities during migration to avoid increasing the workload on Exchange Online resources.
- Monitor migration activity: Review migration progress, reports, and logs regularly to identify throttling responses or performance delays.
Following these practices helps administrators manage Exchange Online migration workloads effectively and reduce the impact of throttling during mailbox transfers.
Steps to increase EWS throttling policy limits in Office 365
Manual management of throttling policies in Exchange Online has been discontinued. Previously, these policies were able to be changed with remote PowerShell, but Microsoft has taken away that ability. Though it is possible to ask Microsoft to briefly increase the EWS throttling for you through the Microsoft 365 admin center or with the support of Microsoft support for assistance.
- Sign in to your Microsoft 365 Admin Center account
- Click ‘…Show all’ on the left side menu
- Navigate to ‘Support’ > ‘Help & support’
- Type ‘Increase EWS Throttling Policy’ in the search bar, press the Enter key, then click the ‘Run Tests’ button
- Wait till the diagnostic test completes. Next, choose either 30, 60, or 90 days to disable the EWS Throttling Policy. Ensure to check the acknowledgement checkbox and then click the ‘Update’ button
- Exchange Web Services (EWS) throttling policy updates have been started. It will be completed within 15 minutes.
- After 15 minutes, perform the test (Step 4) to confirm that the throttling has been disabled.
How EWS Throttling Affects Exchange Online Migration
During an Exchange Online migration, migration applications communicate with Microsoft 365 services to access and transfer mailbox data. Exchange Online monitors these requests and may apply throttling when request limits are reached to maintain service availability.
When throttling occurs, administrators may notice different performance-related symptoms during migration, including:
- Migration speed drops during an active batch: A migration may start at a normal pace but slow down significantly after processing a certain amount of data due to request limitations.
- Intermittent connection delays or failures: Connections to source or target mailboxes may experience temporary timeouts, delays, or rejected requests while Exchange Online manages the workload.
- Repeated item retries: Some mailbox items may be attempted more than once before completing successfully because the migration application waits for Exchange Online responses.
- Large mailboxes taking longer to process: Mailboxes with large data volumes or many attachments may experience more noticeable delays compared to smaller mailboxes.
- Repeated delays shown in migration logs: Migration reports or logs may show recurring delays, retries, or throttling-related responses during similar stages of the migration session.
Best Practices When Managing Exchange Online Migration Performance
- Plan migration batches based on mailbox size and workload.
- Maintain sufficient intervals between multiple migration batches.
- Avoid running heavy concurrent Exchange Online activities during migration.
- Monitor migration progress, logs, and reports for delays or throttling responses.
- Reduce unnecessary mailbox processing activities during migration.
- Verify source and target permissions before starting migration.
- Ensure adequate network capacity for the planned migration workload.
- Review migration performance patterns and adjust the workload when required.
Frequently Asked Questions
What is EWS throttling in Exchange Online?
EWS throttling is a Microsoft 365 service protection mechanism that limits application requests to Exchange Online resources. It helps maintain service stability by controlling how applications access Exchange Online data.
How long does an EWS throttling increase last?
When you request relief through the Microsoft 365 Admin Center's diagnostic tool, you can choose to disable EWS throttling for 30, 60, or 90 days. The update typically completes within 15 minutes of your request.
Can EWS throttling affect Exchange Online migration speed?
Yes. EWS throttling can reduce migration throughput by delaying requests, increasing retries, or extending the time required to complete mailbox transfers.
Does disabling EWS throttling remove all Exchange Online migration limitations?
No. Migration performance also depends on factors such as mailbox size, number of mailboxes, network capacity, Microsoft 365 service conditions, and migration workload configuration.
What should I do if throttling is still affecting migration after requesting an increase?
After requesting a throttling increase, allow sufficient time for the change to take effect and verify the updated status using the available Microsoft 365 diagnostic tools. Since Exchange Online is a shared service, throttling responses may still occur depending on the migration workload, mailbox size, and request volume.
If throttling continues, administrators can temporarily pause the migration and resume it later, or adjust the migration workload by using appropriate mailbox batches instead of processing a single mailbox workload at a time. EdbMails supports parallel mailbox migration, which helps distribute the migration workload more effectively.
Can I still adjust EWS throttling limits using PowerShell?
Microsoft has changed how Exchange Online throttling settings are managed, and administrators may no longer be able to directly modify certain throttling policies through remote PowerShell. Depending on the current Microsoft-supported options, administrators can request throttling adjustments through Microsoft 365 administration tools or contact Microsoft Support for assistance.
