Forum Discussion
Exchange System Mailboxes after migration to Exchange 365
Hi ArjanBroekhuizen,
The "extest" and "DiscoverySearchMailbox" mailboxes are system mailboxes in on-prem Exchange, and they serve specific purposes:
extest Mailbox: The "extest" mailbox is created for testing purposes within on-premises Exchange environments. It is not a standard user mailbox but is used for various testing scenarios, like database and connectivity tests. After migrating to Exchange Online, this mailbox typically serves no further purpose. You can consider removing or disabling it to clean up your on-premises environment. However, make sure that it's no longer needed for any specific tests before doing so.
DiscoverySearchMailbox: The "DiscoverySearchMailbox" plays a crucial role in on-premises Exchange for In-Place eDiscovery. It is a dedicated mailbox used for conducting searches and discovering content within Exchange mailboxes, which is essential for compliance and legal requirements. Even after migrating user mailboxes to Exchange Online in a hybrid or coexistence setup, retaining the "DiscoverySearchMailbox" is advisable. Removing it can disrupt eDiscovery and compliance features.
As for the "Mailbox Server" role on your on-premises Exchange server, it is typical for it to continue hosting certain mailbox roles and system mailboxes, even after user mailbox migration to Exchange Online.
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Leon Pavesic
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Hi LeonPavesic
Thanks for your reply.
Do you know why other system mailboxes/arbitration mailboxes are not count as mailboxes? And why are these mailboxes counted as mailboxes, despite they are system mailboxes?
When we don't host mailboxes on-premise, we don't need a license (because it is only a hybrid server). With this 2 mailboxes we do need a license?
Our Exchange 2019 server is only used as relay-server, so our applications can send mail to our users in Exchange 365. So, I think the extest-mailbox is not needed anymore.
Why do we use the DiscoverySearch-mailbox? There are no mailboxes with messages to search for.
Kind regards,
Arjan
Hi ArjanBroekhuizen,
thanks for your update.
The “extest” and “DiscoverySearchMailbox” are indeed system mailboxes, but they serve specific purposes and are treated differently from other system or arbitration mailboxes.Regarding licensing, typically, you don’t need a separate license for system mailboxes.
If your Exchange 2019 server is only used as a relay server, and you’ve migrated all user mailboxes to Exchange Online, you might not need the “extest” mailbox anymore and you can remove it.
The “DiscoverySearchMailbox” is used for In-Place eDiscovery, which is a tool for searching mailboxes in your organization. Even if there are no user mailboxes on-premises, there might be scenarios where the “DiscoverySearchMailbox” is still needed.
If you’re certain that there’s no need for eDiscovery in your on-premises environment, you could also consider removing this mailbox.Please click Mark as Best Response & Like if my post helped you to solve your issue.
This will help others to find the correct solution easily. It also closes the item.If the post was useful in other ways, please consider giving it Like.
Kindest regards,
Leon Pavesic
(LinkedIn)