See explanation below.
Explanation
In the Exchange admin center, navigate to Recipients > Resources.
To create a room mailbox, click
Use the options on the page to specify the settings for the new resource mailbox.
- Room name: Use this box to type a name for the room mailbox. This is the name that's listed in the resource mailbox list in the Exchange admin center and in your organization's address book. This name is required and it can't exceed 64 characters.
- Alias: A room mailbox has an email address so it can receive booking requests. The email address consists of an alias on the left side of the @ symbol, which must be unique in the forest, and your domain name on the right. The alias is required.
- Location, Phone, Capacity: You can use these fields to enter details about the room. However, as explained earlier, you can include some or all of this information in the room name so users can see it.
When you're finished, click
Reference:
https://docs.microsoft.com/en-us/exchange/recipients/room-mailboxes?view=exchserver-2019