You need to sign is as administrator at the Exchange Administration Centre (EAC) of the Microsoft Online Portal to create a Conference room mail box (or an Equipment or another Resource mail =box)
- In the EAC, navigate to Recipients > Resources.
- To create a room mailbox, click New > Room mailbox.
- Use the options on the page to specify the settings for the new resource mailbox.
After you create a room mailbox or equipment mailbox, you manage its settings by editing the resource mailbox using EAC.
- Room name (Mandatory field) 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 EAC and in your organization's address book. This name is required and it can't exceed 64 characters. Although there are other fields that describe the details of the room, for example, Location and Capacity, consider summarizing the most important details in the room name using a consistent naming convention. This will enable the users to see easily the details when they select the room from the address book in the meeting request.
- Email address (Mandatory field) 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 email address is required.
- Organizational unit - You can select an organizational unit (OU) other than the default (which is the recipient scope). If the recipient scope is set to the forest, the default value is set to the Users container in the Active Directory domain that contains the computer on which the EAC is running. If the recipient scope is set to a specific domain, the Users container in that domain is selected by default. If the recipient scope is set to a specific OU, that OU is selected by default. To select a different OU, click Browse. The dialog box displays all OUs in the forest that are within the specified scope. Select the desired OU, and then click OK.
- 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.
- Booking requests Use this section to configure how the room mailbox handles reservation requests.
Delegates If you selected the option requiring that booking requests are sent to delegates, use this section to select delegates. To add a delegate, click Add. On the Select Delegates page, select a user, click Add, and then click OK to return to the New room mailbox page.
- Automatically accept or decline booking requests A valid meeting request automatically reserves the resource. If there's a scheduling conflict with an existing reservation, or if the booking request violates the scheduling limits of the resource, for example, the reservation duration is too long, the meeting request is automatically declined.
- Select delegates to accept or decline booking requests The delegates are responsible for accepting or declining meeting requests that are sent to the room mailbox. If you assign more than one resource delegate, only one of them has to act on a specific meeting request.
Thereafter, end-users will be able to select this Room (and automatically its email address) when they send a meeting request.
A similar procedure is carried out to create an Equipment mail box or any other resource mail box in Exchange online.