Exchange ActiveSync folder mapping

A long time ago Jim Martin wrote an excellent article how Exchange maps folder IDs for ActiveSync:

MVP Glen Scales wrote a script, which uses Exchange Web Service, to query a mailbox and export the information into a CSV file. Glen’s post could be found here.

Lately I had to troubleshoot Exchange ActiveSync devices and had also the need of mapping IDs to folder as the IIS logs contain only the folder IDs. Glen’s script was doing a good job, but wasn’t too user-friendly. Therefore I improved the usability and extended the ability of gathering data.

With this I was able to easily troubleshoot my devices by parsing the IIS logs with my script Get-IISStats.ps1 and the new one: Get-EASFolderMapping.ps1


In order to run the script successful, you need the following:

The script

The script supports the following parameters:



EmailAddress The e-mail address of the mailbox, which will be queried.
Credentials Credentials you want to use. If omitted current user context will be used.
Impersonate Use this switch, when you want to impersonate.
Server By default the script tries to retrieve the EWS endpoint via Autodiscover. If you want to run the script against a specific server or endpoint, just provide the name in this parameter. Not the URL!
TrustAnySSL Switch to trust any certificate.
WebServicesDLL Path to DLL, if copied instead of installed.
DeviceID A string, which could be used for filtering.

The output is similar to Glen’s script and contains the following fields:



Mailbox The mailbox, which was queried.
Device The name of the folder of the device underneath ExchangeSyncData

Note: This name is used in the parameter DeviceID for filtering.

AsFolderPath Use this switch, when you want to impersonate.
AsFolderID ActiveSync folder ID as it’s logged in the IIS logs.
MailboxFolderPath Absolute folder path.
AirSyncLastSyncTimeUTC Last time in UTC when the device synced the folder.
AirSyncLocalCommitTimeMaxUTC This property has the same value as PR_LOCAL_COMMIT_TIME_MAX of the synced folder

How does it work?

As described in Jim’s article, for every Exchange ActiveSync device a folder is created in the folder ExchangeSyncData like in this example:


Each of this folders contains for each for syncing marked folder a subfolder with a number (the folder ID logged in the IIS logs) and additional system folders:

  • Autod
  • FolderIdMapping
  • Policy
  • Root
  • SyncStatus


Now comes the interesting part:

Each folder contains an item with a messageclass Exchange.ContentsSyncData. We are looking for the following properties:

  • AirSync:AirSyncLastSyncTime (0x81BC0014)

This property is stamped with the latest timestamp the device synced this specific folder

  • AirSync:AirSyncLocalCommitTimeMax (0x81BD0014)

This property has the same value as the folder’s property PR_LOCAL_COMMIT_TIME_MAX, which contains the time of the most recent message change within the synced folder.

Now when you run the script it looks like this:


Does it work in Exchange Online?

Yes, the script supports also Exchange Online. But here things are a bit different:

There is still the folder ExchangeSyncData, which contains for each device a folder, but there are no subfolders for each synced folder. The properties are now part of items in device’s folder.





I would like to thank Jim and Glen for their articles, which made mine possible.

I hope this post helps you for future troubleshooting. At least for me it was a huge help gathering these information easily and within a short time.

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