Book a pool vehicle in Outlook: resource mailbox

Almost every office runs Outlook, so sooner or later the pool vehicle ends up there. Usually as a shared calendar where everyone types "Caddy, client Meier". It shows appointments but prevents nothing: two entries for the same morning sit side by side, and whoever reaches the key cabinet first drives.

You can do better with what you already have. Microsoft 365 has resource mailboxes that accept or decline bookings on their own. This post shows how to set a vehicle up that way, which defaults get in the way for vehicles and where Outlook reaches its limits for a fleet.

Shared calendar or resource mailbox

A shared calendar is an ordinary calendar that several people can write to. It checks nothing. Every entry is equally valid, including the duplicate.

A resource mailbox is a mailbox of its own for the vehicle. You invite it to an appointment like a colleague, and it answers by itself: if the slot is free, it accepts. If it's taken, it declines. Exchange has two kinds: room mailboxes for meeting rooms and equipment mailboxes for anything without a fixed location. Microsoft names the company car as an example. For a pool vehicle, the equipment mailbox is the right one.

The mailbox itself doesn't need a licence of its own. But only people with a mailbox in your Microsoft 365 can book. We'll come back to that below.

Setting up the vehicle as a resource

Whoever manages Microsoft 365 for you does this in the Exchange admin center:

Under Recipients, open Resources and choose Add an equipment resource.
Enter a Name, ideally with the number plate: "Caddy HB-XY 123". Everyone sees the name in the address book, so it should make the vehicle unambiguous.
Pick an email address for the vehicle, such as caddy@your-company.com.
Set the limits under Booking options, more on that in a moment.
Under Booking delegates, decide: either the vehicle accepts requests automatically, or every request goes to a person who approves it.

After that, booking works like any appointment in Outlook: create a new event, enter the time, invite the vehicle by its name as an attendee, send. The reply arrives within seconds as an acceptance or a decline. Room finder doesn't help here, it only lists rooms.

Three defaults that get in the way for vehicles

Resource mailboxes are built for meeting rooms. Three of their defaults don't fit vehicles.

Maximum duration of 24 hours. Out of the box, a booking can last one day at most. The business trip from Monday to Wednesday is declined automatically, and nobody understands why. Set the maximum duration to match your longest trips.

Subject and body are deleted. When the mailbox accepts a request automatically, it replaces the subject in the vehicle's calendar with the organiser's name and removes the text of the invitation. "Oldenburg site, pick up material" becomes "Jana Krüger". Where the trip went is no longer visible in the vehicle's calendar. This can only be switched off in PowerShell:

Set-CalendarProcessing -Identity "caddy@your-company.com" -AddOrganizerToSubject $false -DeleteSubject $false -DeleteComments $false -MaximumDurationInMinutes 4320

The 4320 minutes in the example are three days. For colleagues to actually see the subject, the vehicle's calendar also needs sharing permissions beyond free/busy. By default, others only see availability.

180 days ahead. The vehicle accepts nothing further out. For most fleets that's fine. If you want to block the van for next July's summer party, you have to widen the booking window.

Approval instead of auto-accept

For the small car, automatic acceptance is enough. For the van that only certain people should drive, add a booking delegate. Every request then goes to that person, who accepts or declines. With several delegates, one answer is enough.

Exchange can also restrict booking to specific people or groups. That's possible in PowerShell and a real strength of Outlook: a vehicle meant only for the construction crew declines requests from everyone else.

Where Outlook stops for a fleet

The resource mailbox solves the double-booking problem. It isn't built for the rest of fleet management.

Only people with a mailbox can book. The yard worker without a company email, the temp, the volunteer or the colleague from a partner company aren't in the address book. They call or message someone who books for them.
No odometer reading. Outlook knows who booked the vehicle. How many kilometres were driven, how much fuel was left at return and whether there was new damage isn't recorded anywhere. For that you still need a vehicle logbook and a handover form.
Booked doesn't mean driven. The appointment doesn't record whether the person who booked was behind the wheel. That helps little with a speed camera photo or a dent, as the post on damage to a pool vehicle shows.
Deleted is gone. When someone cancels their appointment, the booking disappears from the vehicle's calendar. A list of who had the vehicle how often last quarter is something you have to build yourselves.
Nothing happens at the vehicle. Someone standing next to the car on short notice opens Outlook on their phone, searches the address book for the vehicle and invites it. It works, but hardly anyone does it.

If double bookings are your only problem and every driver has a mailbox, Outlook is enough. A resource mailbox takes ten minutes to set up and costs nothing extra.

How to do this in Dispoly

Dispoly replaces the resource mailbox, not Outlook. Bookings happen in Dispoly and still show up in your own calendar.

Booking without a mailbox. Members of your organisation book in Dispoly. Anyone without an account books through a booking page or the QR code at the key cabinet. There is no per-person licence, pricing is flat.

No double bookings. Dispoly rejects a second booking for an occupied time slot, just like the resource mailbox. A booking can last up to 90 days and be up to two years ahead, so the three-day business trip goes through without changing anything.

Approval. New categories are created with "Require admin approval for reservations" already ticked. Each vehicle can override that under "Approval Required", for example "Auto-approve" for the small car. Booking rights limited to a specific group, as Exchange offers, don't exist in Dispoly. Every member can request every vehicle, and approval is the control.

Odometer at pickup and return. Under "Pickup & return" you define what is asked when a vehicle is picked up and brought back: the odometer reading and your own fields such as fuel level, damage or who actually drove. In the logbook export, the driver has their own "Driver" column, separate from "Booked by". Anyone who scans the QR code at the vehicle records the reading without logging in. What that looks like day to day is in Record mileage with a QR code.

Still visible in Outlook. Every vehicle has a calendar feed. On the detail page, "Enable calendar feed", copy the link and paste it in Outlook under Add calendar and Subscribe from web. Data flows in one direction only: an appointment someone creates in Outlook doesn't reach Dispoly. Outlook refreshes subscribed calendars several times a day, not instantly. The details are in Calendar sync setup.

Moving over. You can export your existing bookings from classic Outlook for Windows as CSV and check them with the booking check. It recognises the columns of the Outlook export, shows double bookings and creates a "Dispoly import" sheet that you upload under "Import reservations".

What Dispoly can't do here

No connection to Exchange. Dispoly doesn't read Outlook calendars or write to them. The feed is a subscription, not a sync.
No invitations from Outlook. Anyone used to inviting the vehicle to an appointment books in Dispoly from now on. That's a change, and it only works if Outlook is switched off as a booking channel.
No booking rights per group. See above, approval is the control.

Booking a pool vehicle in Outlook: set up a resource mailbox and know where it stops

Shared calendar or resource mailbox

Setting up the vehicle as a resource

Three defaults that get in the way for vehicles

Approval instead of auto-accept

Where Outlook stops for a fleet

How to do this in Dispoly

What Dispoly can't do here

Further reading

End the booking chaos today.

Shared calendar or resource mailbox

Setting up the vehicle as a resource

Three defaults that get in the way for vehicles

Approval instead of auto-accept

Where Outlook stops for a fleet

How to do this in Dispoly

What Dispoly can't do here

Further reading