What's the detailed version of your Exchange servers? Do you have the hybrid or pure on-premises environment?
Does "opening or mounting to specified users" mean the calendar can be displayed automatically for specified users in OWA and Outlook?
If I misunderstood, please point out.
If so, we have to share this resource mailbox calendar to those specified users. After they accepted the shared calendar, it will be displayed automatically both in OWA and Outlook, even when users create a new outlook profile. However, most of these operations cannot be performed from EMS.
Here is my test result in my Exchange 2016 organization:
- Grant Full Access permission to one user to operate the calendar of a resource mailbox Add-MailboxPermission -Identity <resource mailbox> -User <user name> -AccessRights FullAccess -InheritanceType All
2) We can go to OWA to share the resource calendar, it's not supported to share with EMS. Login to the user mailbox > Open another mailbox > enter the resource mailbox name > Calendar > right click the calendar > Sharing permissions. Then we can share the calendar and send emails to specified users:
3) Your users have to accept the message:
4) Then they will see that the resource calendar shows automatically both in Outlook and OWA:
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