Exchange Online Mailboxes still receiving mail without a license.

Sam Brink 1 Reputation point
2022-10-21T09:30:05.39+00:00

I am currently running a hybrid MS 365 environment using AD connect to sync.

Scenario;

UserA

User mailbox was migrated from on-prem Exchange server to Exchange Online

I remove the license and lock the account via AD

I send email to user A and it still delivers.

UserB

User was created in AD and after the AD Sync I created the mailbox on M365.

I remove the license and lock the account.

I send email to user A I get an NDR.9 Which is the desired result .

Why are my migrated accounts still accepting mail?

We don't delete accounts, we disable them for audit and record keeping

Sincere thanks!

Microsoft Exchange Hybrid Management
Microsoft Exchange Hybrid Management
Microsoft Exchange: Microsoft messaging and collaboration software.Hybrid Management: Organizing, handling, directing or controlling hybrid deployments.
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  1. Andy David - MVP 134K Reputation points MVP
    2022-10-21T11:23:42.307+00:00

    When you remove the license for a regular user mailbox, the mailbox doesnt necessarily go away immediately ( I Assume that is what you want).
    It may take some time and is actually recoverable for 30 days:

    https://learn.microsoft.com/en-us/microsoft-365/admin/manage/remove-licenses-from-users?view=o365-worldwide

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  2. Vasil Michev 85,641 Reputation points MVP
    2022-10-21T11:25:25.37+00:00

    If you want to prevent message delivery, use a mail flow rule. As long as the mailbox still exists, it will keep receiving messages regardless of whether it has license or not.
    There are many scenarios is which a mailbox will exist even when you remove the Exchange license, such as when it was put on hold, shared/resource mailboxes, migrated mailboxes in the grace period, etc.

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  3. Joyce Shen - MSFT 16,581 Reputation points
    2022-10-24T06:51:46.44+00:00

    Hi @Sam Brink

    Is there any update here about your question?

    I agree with the method shared above using a mailflow rule to reject the message sent to that account. And according to my research, I found this thread discussed the similar question: E3 license removed but mailbox still receives mail.

    It shared a solution: Remove the proxy addresses from on-premise AD account.

    If an Answer is helpful, please click "Accept Answer" and upvote it.

    Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

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