Added Files

Powershell/PowerShell-Office365Admin/Exchange/FindUsersWithMismatchedDomains.ps1

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+# Find mailboxes where UPN domain doesn't match email domain
+#
+
+# Establish a session to Exchange Online
+$credentials = Get-Credential -Message 'Enter your Exchange Online administrator credentials'
+$connectionParams = @{
+    'ConfigurationName' = 'Microsoft.Exchange';
+    'ConnectionUri' = 'https://outlook.office365.com/powershell-liveid/';
+    'Credential' = $credentials;
+    'Authentication' = 'Basic';
+    'AllowRedirection' = $true
+} 
+$exchangeSession = New-PSSession @connectionParams
+Import-PSSession -Session $exchangeSession
+
+# Get list of mailboxes with a different mail domain to UPN domain
+Get-Mailbox -ResultSize Unlimited | Where-Object {$_.UserPrincipalName.Split('@')[1] -ne $_.PrimarySmtpAddress.Split('@')[1]} | Format-Table Name,UserPrincipalName,PrimarySmtpAddress,RecipientTypeDetails
+
+# Disconnect from Exchange Online
+Remove-PSSession $exchangeSession