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Converting Folder and ItemIds from the Exchange Management Shell and Audit Log entries using PowerShell and the Graph API in Exchange Online

First a little news about Exchange Identifiers that you may have missed (its not often that something like this changes so its rather exciting)

When you access an item in an Exchange Mailbox store whether its OnPrem or in the Cloud you use the Identifier of the particular item which will vary across whatever API your using. Eg

MAPI - PR_EntryId eg NameSpace.GetItemFromID(EntryId)
EWS -  EWSId eg EmailMessage.Bind(service,ewsid)
Rest -   RestId  eg'restid')
The advice over the years has always been its not a good idea to store these Id's in something like a database because they change whenever and Item is moved. Eg if an Item is moved from the Inbox to a Subfolder in the Inbox it will received a different Id so whatever you have stored in your database suddenly becomes invalid and its not easy to reconcile this. However a new feature that has appeared in Exchange Online in Beta with the Graph API is immutableId's see the idea behind this is that this Id doesn't change regardless of which folder the item is moved to (or even if its deleted). While it still in Beta at the moment this is a good feature to use going forward if your building synchronization code. Along with immutableId's an operation to Translate Id's between the EntryId, EWS and REST formats is now available in beta in the Graph which is great if your looking to Migrate your MAPI or EWS apps to use the Graph API 

As Audit records are a hot topic of discussion this week with this post from Microsoft another Identifier format you see when using the Exchange Management Shell cmdlets like Get-MailboxFolderStatics is something like

or in an ItemId in a  AuditLog Record like

With these Id's there are just a base64 encoded version of the EntrydId with a leading and trailing byte. So to get back to the Hex version of the Entryid you might be familiar with from a Mapi Editor you can use something like the following

$HexEntryId = [System.BitConverter]::ToString([Convert]::FromBase64String($_.FolderId.ToString())).Replace("-","").Substring(2)  
$HexEntryId =  $HexEntryId.SubString(0,($HexEntryId.Length-2))

This would turn something like




Just having the Id in whatever format isn't much good unless you can do something with it, so I've created a simple Graph script that uses the new operation to allow you to translate this Id into an Id that would be useable in other Graph requests. I've create a basic ADAL script version an posted it here on my GitHub

A quick Demo of it in use eg Translate a RestId into an EntryId

Invoke-TranslateExchangeIds -SourceId "AQMkADczNDE4YWE..." -SourceFormat restid -TargetFormat entryid
By default the operation returns a urlsafe base64 encoded results (with padding) so in the script I decode this to the HexEntryId which I find the most useful.

I've also cater for allowing you to post a HexEntryId and the script will automatically encode that for the operations eg

Invoke-TranslateExchangeIds -SourceHexId "00000000BE1CDD3D9606274890F3DE4B7DDFBE49..." -SourceFormat entryid -TargetFormat restid
And it also caters for the encoded EMS format and will strip the extra bytes and covert that eg

Invoke-TranslateExchangeIds -SourceEMSId  $_.FolderId.ToString() -SourceFormat entryid -TargetFormat restid
I've also added this to my Exch-Rest module which is available from the PowerShell Gallery and GitHub which is useful if you want to do some following type things. eg if you wanted to bind to the folder in question you could use

$folderId = Invoke-EXRTranslateExchangeIds -SourceEMSId  $_.FolderId.ToString() -SourceFormat entryid -TargetFormat restid
Get-EXRFolderFromId -FolderId $folderId
Need help with anything I've talked about in this post or need somebody to write C#,JS, NodeJS, Azure or Lambda functions, Messaging DevOps or PowerShell scripts then I'm available now for freelance/contract or fulltime work so please drop me an Email at

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All sample scripts and source code is provided by for illustrative purposes only. All examples are untested in different environments and therefore, I cannot guarantee or imply reliability, serviceability, or function of these programs.

All code contained herein is provided to you "AS IS" without any warranties of any kind. The implied warranties of non-infringement, merchantability and fitness for a particular purpose are expressly disclaimed.