Best practice to create room mailbox in Exchange Hybrid setup

Question

Best practice to create room mailbox in Exchange Hybrid setup

Prabhash Jena 21

Hi,

I am running Exchange Hybrid setup, Exchange 2019 with Exchange online. All our mailboxes (user\shared\room etc.) are migrated to Exchange online. All the users & room mailboxes has 'IsDirSynced' property value of 'TRUE'. AzureAD connect is in place for AD sync.
Now I want to cerate new Room Mailbox. Shall I create it in Exchange Online EAC directly or on On-prem Exchange ECP?
Anybody has some tips about what would be the best practice going forward to create Room\Shared mailbox?

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Answer accepted by question author

Andy David - MVP 160.3K MVP Volunteer Moderator

Unless you have some reason you need to create the remote mailbox on-prem , then I would create directly in Exchange Online.

However, if you want to manage the Properties of the room with on-prem EAC or powershell the same as the user maiboxes, create it on-prem.

Its really up to you, there is no best practice.

Prabhash Jena 21 Reputation points

2021-05-10T14:21:37.253+00:00

Thank you for the tip @Andy David - MVP
What is your take on Shared mailboxes?
I was wondering why this article says I should use the on-premises Exchange admin center (EAC) to create and manage shared mailboxes - https://learn.microsoft.com/en-us/microsoft-365/admin/email/create-a-shared-mailbox?view=o365-worldwide
Andy David - MVP 160.3K Reputation points MVP Volunteer Moderator

2021-05-10T15:21:45.663+00:00

Because it would keep things consistent. Your user mailboxes were created on-prem yes? then migrated to Exchange Online?
If you create the remote shared mailboxes on-prem you can manage them on-prem as well - just like the user mailboxes.

However, there is no absolute requriement to do that. You can create them directly in Exchange Online. Really up to you.
Gavin 1 Reputation point

2026-07-10T16:50:55.65+00:00

@Andy David - MVP how does this work where there are mailboxes both on-prem and online that need to book meeting rooms? We'd like to host these in Online but still have them visible in the GAL for on-prem access.

2 additional answers

Prabhash Jena 21 Reputation points

2021-05-10T14:21:37.253+00:00

Thank you for the tip @Andy David - MVP
What is your take on Shared mailboxes?
I was wondering why this article says I should use the on-premises Exchange admin center (EAC) to create and manage shared mailboxes - https://learn.microsoft.com/en-us/microsoft-365/admin/email/create-a-shared-mailbox?view=o365-worldwide
Andy David - MVP 160.3K Reputation points MVP Volunteer Moderator

2021-05-10T15:21:45.663+00:00

Because it would keep things consistent. Your user mailboxes were created on-prem yes? then migrated to Exchange Online?
If you create the remote shared mailboxes on-prem you can manage them on-prem as well - just like the user mailboxes.

However, there is no absolute requriement to do that. You can create them directly in Exchange Online. Really up to you.
Gavin 1 Reputation point

2026-07-10T16:50:55.65+00:00

@Andy David - MVP how does this work where there are mailboxes both on-prem and online that need to book meeting rooms? We'd like to host these in Online but still have them visible in the GAL for on-prem access.

Answer 1

Stefan Rottler 1

You may find this helpful:
https://answers.microsoft.com/en-us/msoffice/forum/msoffice_o365admin-mso_exchon-mso_o365b/room-mailbox-in-hybrid/ce04b900-5fab-4657-9cba-6bd909f73511

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Answer 2

Lucas Liu-MSFT 6,196

Hi @Anonymous ,
1.For the room mailbox. If you don't need to create a remote mailbox or manage it through On-premises Exchange management tools. You can create it directly in Exchange online. If needed, you could create it on-premises Exchange.

2.For the shared mailbox, I recommend that you first create Shared mailbox in on-premises Exchange server. Because of this known issue I found below, if we create a shared mailbox directly in Exchange online, it will may cause the following problems.
Please refer to: Users in a hybrid deployment can't access a shared mailbox that was created in Exchange Online

1).Users can't open the shared mailbox in Outlook.
2).Users can't view free/busy information for the shared mailbox.
3).Users can't send mail to the shared mailbox.

About remote mailbox, please refer to：Enable-RemoteMailbox

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Lucas Liu-MSFT 6,196 Reputation points

2021-05-05T09:14:13.157+00:00

Hi @Anonymous ,
Do suggestions above help?

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Lucas Liu-MSFT 6,196 Reputation points

2021-05-10T09:09:17.65+00:00

Hi @Anonymous ,
I am writing here to confirm with you how thing going now?

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Prabhash Jena 21 Reputation points

2021-05-10T14:22:22.603+00:00

Thanks for the tip. I was wondering why this article says I should use the on-premises Exchange admin center (EAC) to create and manage shared mailboxes - https://learn.microsoft.com/en-us/microsoft-365/admin/email/create-a-shared-mailbox?view=o365-worldwide
Lucas Liu-MSFT 6,196 Reputation points

2021-05-11T07:48:23.987+00:00

Hi @Anonymous ,
I think it may be because of this known issue I found below, so it's don't recommend that you directly create a shared mailbox in Exchange online. If we create a shared mailbox directly in Exchange online, it will may cause the following problems. Based on the above information, I recommend that you first create Shared mailbox in on-premises Exchange server. But for the Room mailbox, no related issues were found. You could create according to your needs.
For more information: Users in a hybrid deployment can't access a shared mailbox that was created in Exchange Online.

1.Users can't open the shared mailbox in Outlook.
2.Users can't view free/busy information for the shared mailbox.
3.Users can't send mail to the shared mailbox.
Lucas Liu-MSFT 6,196 Reputation points

2021-05-11T07:48:38.217+00:00

In addition, in order to avoid misunderstanding by other community members, I have modified the original answer.
Andy David - MVP 160.3K Reputation points MVP Volunteer Moderator

2021-05-11T11:25:58.883+00:00

That only applies in a hybrid environment with mailboxes on-prem.
Since all the mailboxes are in Exchange Online, this article doesnt apply.
Prabhash Jena 21 Reputation points

2021-09-15T13:19:23.06+00:00

Regrading the article you shared it says it applies to
Exchange Online, Exchange Server 2016 Enterprise Edition, Exchange Server 2016 Standard Edition, Exchange Server 2013 Enterprise, Exchange Server 2013 Standard Edition

We are running Exchange 2019.