Unexpected Microsoft Defender for Office 365 License Requirement for Shared Mailboxes
A question about shared mailboxes brought up the topic of licensing requirements when a tenant has Microsoft Defender for Office 365 (MDO). The news is not good. Once MDO is active, every shared mailbox needs an MDO license, and every user mailbox must also be licensed for MDO (those with E5 licenses are covered). At $5 per month, those MDO licenses can ramp up to a considerable cost. Ouch! https://office365itpros.com/2025/08/11/microsoft-defender-for-office-365/
Comparing Outlook Groups to Shared Mailboxes (2022 Edition)
Outlook groups and shared mailboxes both help small teams work with shared email. The decision as to which to use depends on the exact needs the team has. Some recent changes made by Microsoft to allow users to create new folders and rules in group mailboxes might tilt the decision towards group mailboxes, but shared mailboxes still offer lots of potential. https://practical365.com/outlook-groups-vs-shared-mailboxes/
Unable to delete Shared Mailboxes
We are trying to remove a shared mailbox to convert them into Groups, however we are getting this error message. Error: An Azure Active Directory call was made to keep object in sync between Azure Active Directory and Exchange Online. However, it failed. Detailed error message: Another object with the same value for property proxyAddresses already exists. RequestId : xxxxx The issue may be transient and please retry a couple of minutes later. If issue persists, please see exception members for more information. Can anyone help us why are we getting such error and how to successfully delete the shared mailbox. thank you so much
