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Exchange Online has implemented EAS throttling to manage and maintain optimal performance of the Exchange Online environment in Office 365. For more info about how you can view the access state of the mobile device when you use the Exchange admin center and how to collect EAS logs, see the "More Information" section.
- When a delay in sync occurs, don't repeatedly press the Synchronize button on your mobile devices. Additionally, don't quickly switch folders and repeatedly press the button to sync.
- Wait at least 10 minutes before you take additional action so that the throttling will be automatically removed by the service.
- Switch to manual sync to see whether that works to connect and sync your device with the mailbox. Doing this helps prevent your device from sending too many identical commands.
If the issue isn't resolved, contact your mobile device manufacturer to report and investigate this issue.
Note The implementation of the EAS protocol on the device controls the frequency of commands sent to the service. Microsoft Support can't change the software on the devices. Any updates to the device can only occur through the device manufacturer.
View mobile device detailsFor more information about how to view mobile device details, see View Mobile Device Information for Users.
Collect EAS logsFor more information about how to collect EAS logs, see the following Microsoft Knowledge Base article:
- ResponseHeader together with AccessState : Blocked
- AccessStateReason : SyncCommands or AccessStateReason : RecentCommands
If you examine the timestamps, you can see the commands that are sent repeatedly in a very short time period, which result in the 503 Service Unavailable error. This indicates that a device is performing in a manner that causes the Exchange Online service to enable the throttling protection to prevent the device from affecting the performance of the service.