Article ID: 2748176 - View products that this article applies to.
When you try to sync a mobile device that's using Microsoft Exchange ActiveSync (EAS) with Microsoft Exchange Online in Microsoft Office 365, your device can't connect. Depending on your device, you may get one of the following error messages:
Cannot Get Mail
The connection to the server failed.
Cannot Get Mail
An error occurred while delivering the message.
If you use the Exchange admin center to view the mobile device details or if you collect a synchronization log for the device, you get the following error message:
Unable to open server connection due to a security update.
The Access set by column will contain additional info such as the following:
For steps that Office 365 admins can use to identify this issue in the Exchange admin center, see the "More Information" section.
Too many identical commands
When a mobile device acts in a manner that can adversely affect Exchange Online service performance, the device is put into an Access Denied state for a short time. For example, this occurs if a device sends too many identical sync commands to the service for a particular folder in a very short period.
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.
To work around this issue, follow these steps while you discuss this workaround with your device vendor or carrier:
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:
2461792You can open the log file by using a text editor such as Notepad. In the log file, search for a 503 error that contains the following information:
(https://support.microsoft.com/kb/2461792/ )How collect ActiveSync device logs to troubleshoot sync issues between mobile devices and Exchange Online
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.
Still need help? Go to the Office 365 Community
Article ID: 2748176 - Last Review: July 13, 2014 - Revision: 9.0