Remove calendar processing from a non-resource mailbox

Today I was working on converting an Office 365 room-mailbox to a ‘regular’ shared mailbox. The customer had some legitimate reasons to convert this mailbox, and who am I to question. 😉

Convert Room to Regular using PowerShell

The conversion itself is fairly simple, using PowerShell

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get-mailbox name | set-mailbox -type shared

This sets the mailbox to a ‘regular’ shared mailbox instead of a room mailbox (what it was). After setting some access rights to the mailbox I emailed the customer that his mailbox was changed and that he could access it.

Calendar processing

After a few minutes, I received an email stating that he could send an email to the newly converted shared mailbox, but that the email would be moved to the trash can almost instantly. I know this is the default behavior for room mailbox where the calendar autoprocessing is enabled, so I reverted back to my Powershell window.

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get-calendarprocessing mailbox

This shows that the calendar processing for this mailbox is still active. Apparently, this doesn’t get disabled when converting a room mailbox to a different kind of mailbox. No problem, because we can use the set-calendarprocessing to disable this feature.

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set-calendarprocessing mailbox -automateprocessing:none

Unfortunately, this returns an error:

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AutomateProcessing can only be enabled on resource mailboxes.    
+ CategoryInfo          : InvalidData: (Mailbox:ADObjectId) [Set-CalendarProcessing], ResourceOnlyException    
+ FullyQualifiedErrorId : [Server=DB3PR07MB0489,RequestId=b62184cc-956e-440c-bd97-13ffa4b28872,TimeStamp=15-2-2016    10:56:58] [FailureCategory=Cmdlet-ResourceOnlyException] 
F82DA6B3,Microsoft.Exchange.Management.StoreTasks.SetCalendarProcessing    
+ PSComputerName        : outlook.office365.com

The error is clear: you can only run this command on a resource mailbox. The solution was also clear: convert the mailbox back to a room mailbox, remove the calendar processing and convert the mailbox to a regular shared mailbox again.