Exchange Online Mailboxes still receiving mail without a license.

Question

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!

Answer 1

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

Answer 2

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.

Answer 3

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.

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