Forum Discussion
TonyRedmond
Mar 28, 2025MVP
Duplicate Mail User Objects Created for Guest Accounts
The February 2025 EX1015484 incident explains why mail user objects with duplicate SMTP addresses are created for guest accounts. That’s a problem because Exchange Online can’t route messages to objects with duplicate email addresses. Fortunately, you can find out if any duplicates exist in your tenant with some PowerShell. It's a good opportunity to remind ourselves of the relationship between Entra ID guest accounts and Exchange Online mail user objects.
https://office365itpros.com/2025/03/28/ex1015484-problem/
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