Calendar Problems

How to Manage Exchange Meeting Rooms Across Multiple Microsoft 365 Domains

Elise Williams Oct 10, 2026 869 views

Question details

The user needs to understand how users in separate domains can view and manage meeting rooms in Room Finder when the companies have different security policies.

How to Manage Exchange Meeting Rooms Across Multiple Microsoft 365 Domains

Product: Microsoft Exchange
Device & OS: not provided
Scenario: Coordinating meeting room availability and resource management across different domains and security policies.
Observed behavior: Users from separate domains need access to Room Finder, requiring specific Exchange permissions and organization configurations to bypass visibility limitations.

Before you start

Verify whether the different domains belong to a single Microsoft 365 organization (tenant) or separate tenants, as this determines which Exchange permissions can be delegated.

Solution 1Recommended

Configure Room Delegation in the Same Microsoft 365 Tenant

If both domains reside within the same Microsoft 365 organization, you can assign cross-domain room management permissions through the Exchange admin center.

Cross-domain room management is natively supported as long as all domains are verified under a single Microsoft 365 tenant. The organization's unified structure allows administrators to delegate permissions directly to users regardless of their specific domain suffix.

Access Exchange Admin Center

Log in to the Microsoft 365 admin center using an account with Exchange Administrator privileges, and navigate to the Exchange admin center.

Navigate to Resources

In the left navigation pane, click on 'Recipients' and then select 'Resources' to view all room and equipment mailboxes.

Delegate Permissions

Select the target meeting room, click on 'Manage delegates', and add the users from the separate domain, granting them scheduling or Full Access permissions as dictated by your security policies.

Add to Room Lists

Ensure that the meeting rooms are added to designated Room Lists so they successfully populate in the Room Finder for all users within the organization.

Configure Room Delegation in the Same Microsoft 365 Tenant

Configuration Scope: Changes to delegate permissions and Room Lists may take up to 24 hours to fully sync and reflect in users' Outlook Room Finder.

Solution 2

Open a Microsoft Support Request for Separate Tenants

If the companies operate on entirely separate Microsoft 365 tenants with distinct security policies, standard room delegation will not work and requires Microsoft support guidance.

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Frequently Asked Questions

Why aren't meeting rooms from another domain showing up in Room Finder?

Room Finder relies on Exchange Room Lists. If the domains are on separate tenants, or if the rooms haven't been added to a Room List that your account has permission to view, they will not populate in the Room Finder interface.

Can I grant full access to a room mailbox to a user in a completely different tenant?

No, direct mailbox delegation permissions such as Full Access, Send As, or Send on Behalf are strictly limited to users within the same Microsoft 365 organization (tenant). For separate tenants, external sharing policies or organizational relationships must be utilized.

How do I create a unified Room List for multiple domains in the same organization?

You can create a Room List using Exchange Online PowerShell. Use the 'New-DistributionGroup' cmdlet with the '-RoomList' parameter, then use 'Add-DistributionGroupMember' to add the room mailboxes from various domains into this single list.

Outlook & Email Problems