Exchange Online resource mailboxes

A resource mailbox in Exchange Online represents a physical resource that can be booked through the calendar: a meeting room, a piece of equipment (projector, vehicle, conference robot), a workspace desk. Users invite the resource to a meeting; the resource accepts or declines based on its calendar rules.

Room mailboxes

A room mailbox represents a physical meeting room. Properties include:

• Display name — usually something descriptive like "Conf Room — Engineering Floor 3 — Building A."
• Capacity — number of seats.
• Equipment / features — video conferencing system, whiteboard, projector, accessibility features.
• Location attributes — building, floor, city, GPS coordinates (for richer room finder).
• Booking policy — who can book, max duration, advance booking limit, allow recurring meetings, auto-accept.

The Outlook Room Finder uses these properties to help users filter rooms by capacity, features, and location.

Equipment mailboxes

An equipment mailbox represents bookable equipment — a projector, a parking space, a vehicle, a piece of medical equipment, an instrument. Behaves similarly to a room mailbox but isn't tied to a physical room. Useful for any resource that needs a calendar.

How booking works

When a user creates a meeting and invites a resource:

1. The user sees the resource's free/busy in the scheduling assistant.
2. They send the invite.
3. The resource's mailbox runs calendar attendant — auto-accept rules.
4. If the time is free and the request matches policy, the meeting is accepted automatically.
5. If conflicting or out-of-policy, it's declined automatically with a reason.

Most rooms are configured for auto-accept so users get instant confirmation.

Workspace mailboxes

A newer variant: workspace mailboxes for hot-desking scenarios. A workspace can have multiple bookings on the same time slot (up to its configured capacity), so 10 desks in a workspace mailbox can have 10 different bookings overlapping. Used with Microsoft Places for hybrid-work desk booking.

Configuration

In the Exchange admin center under Recipients → Resources:

1. Create the resource mailbox.
2. Set properties — display name, capacity, equipment list, location.
3. Configure booking policy — auto-accept, working hours, advance booking limit, max meeting duration, allow recurring, who can book.
4. Configure room lists — group rooms by building/floor for Room Finder.
5. Configure equipment rooms with the right list of features (video conf hardware, whiteboard, etc.).

Common pitfalls

• Time zone misconfiguration — rooms across regions need their time zone set correctly.
• Working hours wrong — out-of-hours requests get declined; if you allow 24/7 booking, configure the resource accordingly.
• Recurring meetings booked forever — set a sensible max recurring meeting length.
• Auto-accept with conflicts — for high-demand rooms, decide between "first request wins" or "manual approval by an admin."
• Capacity not enforced — a resource mailbox doesn't strictly prevent more attendees than capacity; that's organisational discipline.

Reporting

Use Microsoft Places or third-party analytics to track:

• Room utilisation by floor / building.
• No-show rate (booked but not attended).
• Peak booking times.
• Over-/under-used rooms.

This data drives real estate decisions — which rooms to repurpose, where to add capacity, what room sizes are actually used. For hybrid-work organisations, room data is increasingly part of facility strategy.