SEMblog

Recently at a client we configured some mailboxes as Resources. 
It was then decided that they would be better off as shared mailboxes, as they could be used for other tasks. Therefore the mailbox was converted to shared:

set-mailbox mailboxname -type:shared

However any emails sent to the new Shared mailbox were continuing to go in to the Deleted Items folder. This is the standard behaviour for a resource mailbox, as it is only expecting to get calendar items. 

The key is to disable the Calendar processing. You can see the current setting thus:

get-calendarprocessing mailboxname | select identity, AutomateProcessing

To disable it completely, you need to change the value of AutomateProcessing to none

set-calendarprocessing mailboxname -AutomateProcessing None

In this case, the folder still needed to accept and process calendar entries, so we changed it to AutoUpdate.

set-calendarprocessing mailboxname -AutomateProcessing AutoUpdate

The full parameters are discussed in the Technet article:

http://technet.microsoft.com/en-us/library/dd335046(v=exchg.141).aspx

Kudos to Holly at the client for finding the value which I had completely forgotten about!