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Modifying your Exchange Online PowerShell Managed Code to use oAuth and MSAL

While not as popular these days many .net developers may have in the past used Managed code to run Exchange Online PowerShell cmdlets to do things like assign Mailbox Permissions or run other EXO PowerShell Cmdlets to get reporting information where no other alternatives where available (or are still available). The majority of these code bases are most likely using basic authentication using something like


In this post I'm going to cover how to change your existing code, you might want to consider however making use of some of the new ExchangeV2 Powershell module functionality to improve performance and security . But to migrate existing code to use oAuth from Basic Authentication is relatively straight forward
  1. You will need some code to do the Authentication, for this I'm going to use the MSAL library because its both the recommended library from Microsoft and its easy to use. 
  2. You should create your own Azure App registration and consent to it that has the Exchange.Manage Permissions eg


(If you can't create your own app registration you can use the well-known ClientId from the V2 PowerShell Module which I've used in the below samples).

Once you have your authentication code generating a Token you then use that as the Password in the PSCrednetial object you pass in the WSManConnectionInfo object. The one thing you need to change is the WSManConnection URI to include the parameters DelegatedOrg which should be set to your domain and add  BasicAuthToOAuthConversion=true eg so your connection string should look like
https://outlook.office365.com/powershell-liveid?DelegatedOrg=youdomain.onmicrosoft.com&BasicAuthToOAuthConversion=true
eg an Interactive Auth sample to run Get-Mailbox would look like 

If you need your code to run non-interactively with a set of credentials you can use the ROPC grant like

 



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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.