Exchange 2013 appointments accepted as tentative without user's knowledge

Question

I have a user who is saying meetings appear on his calendar without him accepting them. He never sees the invitation in his inbox either. I have verified this by sending him a test invitation. He is a Mac user running Outlook 2011, to my knowledge this client cannot perform auto-accept, but just to make sure I had him close Outlook and launch OWA, then sent a second test invitation. This one was also auto accepted.

I checked to make sure there were no server side rules attached to his account (and no client side in Outlook). Below is the output of get-CalendarProcessing for his account. I don't think there is an issue with any of these settings. They are identical to other users who are not having this issue.

[PS] C:\Windows\system32>Get-CalendarProcessing *username*|fl

RunspaceId                          : b6f805f6-41ef-4375-aa05-0323fe7daa24
AutomateProcessing                  : AutoUpdate
AllowConflicts                      : False
BookingWindowInDays                 : 180
MaximumDurationInMinutes            : 1440
AllowRecurringMeetings              : True
EnforceSchedulingHorizon            : True
ScheduleOnlyDuringWorkHours         : False
ConflictPercentageAllowed           : 0
MaximumConflictInstances            : 0
ForwardRequestsToDelegates          : True
DeleteAttachments                   : True
DeleteComments                      : True
RemovePrivateProperty               : True
DeleteSubject                       : True
AddOrganizerToSubject               : True
DeleteNonCalendarItems              : True
TentativePendingApproval            : True
EnableResponseDetails               : True
OrganizerInfo                       : True
ResourceDelegates                   : {}
RequestOutOfPolicy                  : {}
AllRequestOutOfPolicy               : False
BookInPolicy                        : {}
AllBookInPolicy                     : True
RequestInPolicy                     : {}
AllRequestInPolicy                  : False
AddAdditionalResponse               : False
AdditionalResponse                  :
RemoveOldMeetingMessages            : True
AddNewRequestsTentatively           : True
ProcessExternalMeetingMessages      : False
RemoveForwardedMeetingNotifications : False
MailboxOwnerId                      : *********
Identity                            : *********
IsValid                             : True
ObjectState                         : Changed

What else can I check? What am I missing? Any assistance would be appreciated.

Solution

It's the Exchange server's 'Calendar Attendant' that's doing it, not the Outlook client.

There are three ways to disable the 'Calendar Attendant'.

In the Outlook CLient

You can disable the functionality from the Outlook client, but I don't think the option exists in Outlook 2011 for Mac.

In OWA - Outlook Web Access

1. Log into OWA using the address provided by your Exchange Administrator.
2. Click Options in the top-right corner of the window and then choose See all options...
3. Choose Settings and then select the Calendar tab
4. Uncheck the box for Automatically place new meeting requests on my calendar, marked Tentative

Source for steps

Using the Exchange Powershell console

Alternatively you should be able to disable them per-user from the Exchange server itself (Source):

Set-CalendarProcessing -Identity "user name" -AddNewRequestsTentatively:$false

Note that changing this parameter is only supported for resources (rooms, equipments, ...). To disable it for regular user, one has to temporarily change the account type (Source).

Get-Mailbox -Identity "user name" | Set-Mailbox -Type Room
Get-Mailbox -Identity "user name" | Set-CalendarProcessing -AddNewRequestsTentatively:$false
Get-Mailbox -Identity "user name" | Set-Mailbox -Type Regular

If you want to completely disable the calendar attendant, set AutomateProcessing to 'none':

Get-Mailbox -Identity "user name" | Set-Mailbox -Type Room
Get-Mailbox -Identity "user name" | Set-CalendarProcessing -AutomateProcessing:'none'
Get-Mailbox -Identity "user name" | Set-Mailbox -Type Regular

Comments

[Ƭᴇcʜιᴇ007]

Are they being added as "Accepted" or "Tentative"? What permissions do you (and others sending appointments) have to the user's Calendar?

[Jeff Gillis]

They are being added as tentative. I have full access, but others have no special permissions and there are no delegates to this mailbox.

[Ƭᴇcʜιᴇ007]

so it's not actually auto-accepting them at all. Please edit your question to accurately reflect what's going on and what you're trying to solve.

[Jeff Gillis]

Title edited. Constructive suggestions?

[Jeff Gillis]

I don’t see that option in OWA for Exchange 2013. When I run the Powershell command I receive the following error message. AddNewRequestsTentatively can only be enabled on resource mailboxes. + CategoryInfo : InvalidData: (.com/HK/HK.../Users/:ADObjectId) [Set-CalendarProcessing], Re sourceOnlyException + FullyQualifiedErrorId : [Server=**,RequestId=3ea34bd2-ab91-497c-b222-38a3355e1668,Ti‌​meStamp=1/9/2015 1:21 :26 PM] [FailureCategory=Cmdlet-ResourceOnlyException] 1212B1FC,Microsoft.Exchange.Management.StoreTasks.SetCalend arProcessing

[Ƭᴇcʜιᴇ007]

@Jeff Interesting stuff. I edited my answer with some more info I dug up.

[Martin Monperrus]

By temporarily changing the account type to "room", this parameter can be changed, see edited answer.