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!

Exchange | Hybrid management
{count} votes

3 answers

Sort by: Most helpful
  1. Andy David - MVP 157.8K Reputation points
    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

    0 comments No comments

  2. Vasil Michev 119.9K Reputation points MVP Volunteer Moderator
    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.

    0 comments No comments

  3. Joyce Shen - MSFT 16,701 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.

    0 comments No comments

Your answer

Answers can be marked as Accepted Answers by the question author, which helps users to know the answer solved the author's problem.