Note: this will stop Outlook and Exchange from creating tentative appointments on the calendar automatically, however, the tentative appointment will be created at the time you select the meeting request in your Inbox.
AddNewRequestsTentatively only works with resource mailboxes in newer versions / builds of Exchange server, including Office 365's Exchange Online.
Exchange Server 2013
The administrator can use this cmdlet to prevent tentative appointments meeting requests received from users outside of your network.
Set-CalendarProcessing -Identity "your name" -AddNewRequestsTentatively:$false
This cmdlet will block external meeting requests.
Set-CalendarProcessing -Identity "your name" -ProcessExternalMeetingMessages $false
Change Outlook options for Tentative Appointments
You can configure two Outlook options to reduce the annoyance level of meeting spam.
In Options > Calendar, turn off default reminders. While this will affect appointments you create, you can use an ItemAdd macro to set reminders on appointments marked busy.
If using POP3, IMAP, or Outlook Connector accounts, you can turn off the 'sniffer'. With the 'sniffer' enabled, the meeting request is automatically added to the calendar as tentative a few minutes after arrival. When it is disabled, a tentative appointment is added to the calendar when you select or open the meeting request.
Turn off the sniffer at File > Options > Mail > Tracking section (Outlook 2010/2013) or Tools > Options > Email options > Tracking, do not select the option to process requests and responses on arrival.
OWA
Depending on the version of Exchange server, users may be able to also control this setting in OWA. In Options, Setting, Calendar, under Automatic Processing, disable the option to Automatically place new meeting requests on the calendar as Tentative appointments. This is not available in Outlook on the web (Office 365).
(Click on image to view full dialog.)
I have set AddNewRequestsTentatively to $false. Exchange still adds appointments as tentative to the rooms calendar. I guess this Feature is not working on Exchange 2013!?
It should work in 2013... but it wouldn't work for rooms as the calendar attendant processes the meeting requests.
Cmdlet will only work on a room resource not a users mailbox
Correct, in current versions, it only works on resources.
The versions/builds available when the article was written could apply it to all mailboxes. They made changes to the sniffer to improve consistency - not creating tentative appointments affected the consistency for end users.
Hello, this options in OWA was removed at Office 365.
Hi, Diane
I'd like to invite several people to an Outlook meeting. When receiving the invitation, these people should not be able to click on the tentative button. In other words, the tentative button should be disabled or at best not even be displayed. Is there a way to do that?
Thanks in advance for your reply.
Best regards
No, it can't be removed for a single event. The admin can disable it for all events (by removing the tentative command from the ribbon).
huge help thank you :0)