Microsoft Graph API Powershell Example - App with Secret

Microsoft Graph API Example - App with Secret.ps1

#Require an AzureAD App with Microsoft Graph API and
# App Permission
#   - Read mail in all mailboxes
# Impersonation Permission  
#   - Read user and shared mail
# Don't forget to grant permission

#Pre-reqs for REST API calls
$ClientID = "XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX"
$ClientSecret = "XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX="
$user = "user@TENANTNAME.onmicrosoft.com"
$tenantdomain = "TENANTNAME.onmicrosoft.com"

#API info
$loginURL = "https://login.microsoftonline.com/"
$resource = "https://graph.microsoft.com"

# Get an Oauth 2 access token based on client id, secret and tenant domain
$body = @{grant_type="client_credentials";resource=$resource;client_id=$ClientID;client_secret=$ClientSecret}
$oauth = Invoke-RestMethod -Method Post -Uri $loginURL/$tenantdomain/oauth2/token?api-version=1.0 -Body $body

#Let's put the oauth token in the header, where it belongs
$headerParams  = @{'Authorization'="$($oauth.token_type) $($oauth.access_token)"}

#GET 
$uri ="https://graph.microsoft.com/v1.0/users/$($user)/Messages"
$tenantInfo = (Invoke-RestMethod -Uri $uri –Headers $headerParams –Method Get –Verbose).value
$tenantInfo | select Subject