How to collect ActiveSync device logs to troubleshoot sync issues between mobile devices and Exchange Online

Introduction

This article describes how to collect Exchange ActiveSync device logs to troubleshoot sync issues between mobile devices and Exchange Online in Microsoft 365. If you can't sync your mobile device to your mailbox, you may be asked by Microsoft 365 Support to collect logs for troubleshooting.

Procedure

To capture ActiveSync device log information, follow these steps:

1. Connect to Exchange Online PowerShell.

2. Run the Set-CASMailbox cmdlet to enable ActiveSync logging for a specific user:

   Note

   Exchange ActiveSync debug logging is enabled for 48 hours in Exchange Online, and 72 hours in Exchange Server. After the time period expires, the value reverts to $false.

   Set-CASMailbox tony@contoso.com -ActiveSyncDebugLogging $true
   

   Note

   This example enables Exchange ActiveSync debug logging for the user tony@contoso.com.

3. Reproduce the behavior that you want to capture.

4. Run the Get-MobileDeviceStatistics cmdlet to retrieve the log:

   Get-MobileDeviceStatistics -Mailbox TonySmith -GetMailboxLog -NotificationEmailAddresses "admin@contoso.com"
   

   Note

   This example retrieves the statistics for the mobile phone configured to synchronize with the mailbox that belongs to the user Tony Smith. It also outputs the log file and sends it to the System Administrator at admin@contoso.com.

More information

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