How to share Microsoft 365 resources (in our case meeting rooms) with external domain?

Question

How to share Microsoft 365 resources (in our case meeting rooms) with external domain?

Aydin Yusifov 20

Hello. We have 2 meeting rooms in the Microsoft 365 admin center -> resources -> rooms&equipments. We want to share them with other company's users, whith whom we do not have any trust relationships, so they can see which rooms are available and which aren't, also reserve their own meetings if they need. We need synchronization. The addresses of the meeting rooms don't exist as a standalone mailbox.

The only thing we have tried is to make an organizational sharing in the Exchange admin center -> Organizaiton -> sharing. Here we added a new organizational sharing. But it didn't work.

0 comments

Answer accepted by question author

Helen Luu 3,550 Independent Advisor

Hello @Aydin Yusifov

To allow an external user to book a meeting room resource directly, the room mailbox must first be configured to process meeting requests from external senders.

This requires an administrator account with at least the Exchange Administrator role. Please run the following commands in Exchange Online PowerShell:

Connect-ExchangeOnline  

Set-CalendarProcessing -Identity "Lavender" -ProcessExternalMeetingMessages $true

In the example above, "Lavender" is the display name of the room resource. Please replace it with the appropriate room name if necessary.

Once this configuration has been applied, the external user can create a Teams meeting (or Outlook meeting invitation) and add the room's email address as an attendee/resource. The room mailbox should then process the request in the same way as it does for internal users, subject to the room's booking policies and availability.

Could you please give this a try and let me know the outcome? I look forward to hearing from you.

If the answer is helpful, please click "Yes". If you have extra questions about this answer, please click "Comment".

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

Helen Luu 3,550 Reputation points Independent Advisor

2026-10-11T06:59:05.05+00:00

Hello,

I just wanted to follow up and check whether the information above was helpful for you. If you have any new updates, please feel free to share them. Thank you warmly.
Aydin Yusifov 20 Reputation points

2026-10-12T06:29:43.5266667+00:00

Hello, Helen Luu. Thank you for the answer. Yes, this indeed helped, but additionally I did many other things, besides that, and I am not sure if by running this script only would I be able to share the calendar.

Now I am able to add a calendar in the other domain (they need to add the mail of the calendar as a contact), or just create an event and write the mail of the calendar in the place of invited person. I want to share a guide that I found after I posted this question, which helped me a lot, too.

https://www.georgealmeida.com/2024/11/allow-external-users-to-book-meeting-rooms-in-microsoft-365/
Helen Luu 3,550 Reputation points Independent Advisor

2026-10-12T15:47:03.6433333+00:00

Hello,

Thank you very much for your guidance. This information will be extremely helpful for users who want to allow external users from different organizations to book meetings directly or reserve meeting resources without needing to be part of the same organization.

I appreciate you sharing this solution, as it will benefit others who may encounter the same scenario in the future.

1 additional answer

Your answer

Helen Luu 3,550 Reputation points Independent Advisor

2026-10-11T06:59:05.05+00:00

Hello,

I just wanted to follow up and check whether the information above was helpful for you. If you have any new updates, please feel free to share them. Thank you warmly.
Aydin Yusifov 20 Reputation points

2026-10-12T06:29:43.5266667+00:00

Hello, Helen Luu. Thank you for the answer. Yes, this indeed helped, but additionally I did many other things, besides that, and I am not sure if by running this script only would I be able to share the calendar.

Now I am able to add a calendar in the other domain (they need to add the mail of the calendar as a contact), or just create an event and write the mail of the calendar in the place of invited person. I want to share a guide that I found after I posted this question, which helped me a lot, too.

https://www.georgealmeida.com/2024/11/allow-external-users-to-book-meeting-rooms-in-microsoft-365/
Helen Luu 3,550 Reputation points Independent Advisor

2026-10-12T15:47:03.6433333+00:00

Hello,

Thank you very much for your guidance. This information will be extremely helpful for users who want to allow external users from different organizations to book meetings directly or reserve meeting resources without needing to be part of the same organization.

I appreciate you sharing this solution, as it will benefit others who may encounter the same scenario in the future.

Answer 1

How do I get my google mail hosted domain email to be accessible through outlook? I've done everything and it keeps defaulting to me having to open and new @outlook.com or @hotmail.com even though it sees my email address is already in the 365 app and using other apps and I followed the recommended steps and even approved my email to be used and accessed and approved the steps one by one and still keep getting defaulted every time I try to access outlook browser online. It works on my desktop and on my phone but not on the internet through edge I get blocked with a default notice every time trying to get to sign up for outlook email or hotmail email. This issue needs fixed.

What do I do?