Glen's Exchange and Office 365 Dev Blog

This is a continuation somewhat of my previous post on using a generic oAuth script to access EWS but in this post I'm going to look at how you can authenticate as a Guest user to a tenant you have been granted Guest access to and then access the resources like a Unified Office365 Group or Teams( because Teams uses Groups) via the Graph API. To Access another tenant as a Guest (considering that Guest Access is enabled and you have accepted the invitation and logged in at least once with that user) you need to generate an Access Token against the Target tenants endpoints. To do this you can discover what a particular tenants Authentication and Token endpoints are by making a request like the following $RequestURL = " https://login.windows.net/{0}/.well-known/openid-configuration " - f $TargetDomain $Response = Invoke - WebRequest - Uri $RequestURL $JsonResponse = ConvertFrom - Json $Response . Content This will return a result like the following Out of thi

Microsoft recently posted an update that will affect those people who use EWS in applications and script against Office365  https://blogs.technet.microsoft.com/exchange/2018/07/03/upcoming-changes-to-exchange-web-services-ews-api-for-office-365   While 2020 is a few years away what this means is that if you are using Basic Authentication in your EWS scripts or applications that on the 13th October 2020 your app will stop working. Given the amount of time you have and the changes required to support oAuth nobody should really be caught out by this but procrastination and people not understanding legacy applications will mean I'm sure this date won't pass without any infamy. Within PowerShell scripts you have two options to generate the oAuth tokens you need to keep you script working. One is to use a dependency library like ADAL to do it which Ingo posted a really good write up for https://ingogegenwarth.wordpress.com/2018/08/02/ews-and-oauth the other is just create some o