You maybe sharing meeting rooms with your partners and they can use your room when it is not used. The following steps shows you how to share the room with people outside your company:


Preparation Steps (done by administrator)

1.  Add delegate access to people managing the room in your company

From Admin Center > Resources > Rooms & equipment, locate the room you would like to manage and edit Delegates to add the person in your company to share the room's calendar.


 2. Edit exchange settings for the room and give the person a Full Access rights to the room



Sharing Room's calendar (done by the room delegate)

1. From the delegate's account, switch to the room's account

Logon with delegate's account, navigate to the outlook calendar, then open the account (click the profile picture on the upper right corner). Click on "open another mailbox" option.


2. Search and select the room's account which has been delegated to


3. Navigate to the calendar and click Share

Enter the email address of the person to share (note: only Microsoft's email account including Office 365, outlook.com) and select the share option 



Viewing shared room's calendar 

1. The external user will receive an email invitation to view the calendar. Click accept and share calendar.


2. Navigate to the calendar view to see the room's availability



So in other words we can share free/busy with consumer accounts now? Or is this only limited to @outlook.com accounts? And is it Room mailboxes only? What about other recipient types?


I did a quick test and I seem to be able to add the permissions on a room and a shared mailbox to a @gmail.com account, the link however takes me to https://calendar.live.com? So I guess it's only possible with outlook.com users?

Nevermind, got it working for shared mailboxes too. It seems to be just the good old Calendar Publishing though, so what's the new part? :)


Not new - but I have a customer asked me and I could not find an existing article on sharing resource calendar, so thought to share this info on a blog :-)

Got it, thanks :) And yes, it's nice to have a detailed article on this.

Occasional Visitor

Is this also supposed to work with accounts that are no Microsoft accounts? I tried it, but the room/calender on the other account stays empty.

Is there a long delay before you can add the Resource mailbox? I'm in my account on Office 365 in the browser and I've picked Open Another Mailbox but the resource mailbox for the resource I recently created isn't appearing. I'm assuming this is either a delay until it appears because the resource was recently created or you can't do this with resources as they don't use a licence?

Occasional Visitor

I have a room calendar and when an outside person makes an meeting, it shows up on the calendar. But when they change the meeting, it does not reflect the new meeting time on the calendar. They can delete the meeting,

Never got this working. Made myself delegate and opened Outlook online but still can never "Open another mailbox" as it's never in the list.

Senior Member
Welly, Is it at all possible to share a resource "Room" Outside your org to another O365 Org? Can this be done via your steps above, but instead use an Office 365 group from the external org to process permissions to the resource? Or can this only be done individually? (Which I did get working, but would rather not manage permissions this way.) I already have my resources calendar set to process external reservation requests. My business case is that my company shares physical office space with another company (that has O365) and I want to share our resource cal with their Staff_Group@. Thanks!
Established Member

@Patty Allison 


Just to confirm that your outside person can make a room booking and it populates the meeting room calendar? I have followed all the steps, but the outside person can only view the calendar as free/busy, but when they add the meeting room to their calendar invite or invite the meeting room as a user, it does not appear in the meeting room calendar. The outside person also tried to create a calendar entry from the meeting room calendar, but again it only populates the users calendar and not the meeting room calendar.


@Welly Lee can you offer any insights on the above?





Super Contributor

I was wondering if this could possibly be done with Microsoft Bookings offering.

Established Member

@Patty Allison do you have any feedback?


@Keira McCann, have you opened your resource mailbox to allow external to send mails to it?

You need to activate it with: Set-CalendarProcessing -ProcessExternalMeetingMessages $true


@Robert Woods, how should you do this in Microsoft Bookings? Seems not to be a good solution in my eyes... Microsoft Bookings don´t have access to the resource mailbox and then you first need to book your "meeting" in Bookings and then send a proper invite to the users that should be a part of the meeting.

Established Member

@Martin Front thanks for the feedback, unfortunately our security protocols dont allow us to open the resource mailbox to allow external to send mail, I was hoping there was another way as the external users can now View the calendar!