Delete Button Disabled in Outlook 2010 with Exchange 2013

Question

I recently switched from a 3rd party mail software to Microsoft Exchange.  I have had some users ask me why the Delete button is disabled.  I didn't enable any special policy to cause this, and the Delete key on the keyboard will delete messages. 
The disabled Delete button I am referring to is in the Home ribbon and the right-click menu for selected e-mail(s).  Is this standard behavior for Exchange, and can it be changed?

Answer 1

It so happens that I have an XP VM with Outlook 2007.  That having been said, as previously mentioned, before testing, I (thought I) could confirm the same consistent behavior in the following configurations:
WinXP + Outlook 2003
Win7 + Outlook 2010
Each of these systems was using a different user account, and I have tried folderview repairs in EMC to no avail.
Strangely, WinXP + Outlook 2007 does not appear to exhibit the behavior.  In this test case, the profile and OST were just created, but switching to folderview or moving the reading pane to the bottom did not affect the behavior.
Given that information, I proceeded to re-verify, and I hadn't checked winXP + Outlook 2003 because the computer in question had been upgraded to Outlook 2010.  However, I verified the issue does still exist there.  Next, I proceeded to check another
computer that I thought would be WinXP + Outlook 2003, but it had also been upgraded to Outlook 2010.  This computer did not have the issue, and this leads me to a new theory about the cause (but no closer to resolution).  For the record, of the
three computers (two exhibiting the issue, one not), only one has the Adobe plugin mentioned in my last post in response to Diane Poremsky, so the issue doesn't appear to be related to that.
That said, my theory follows:  This is somehow related to IMAP in Outlook 2010.  The computers that exhibit the issue were all previously running IMAP in Outlook 2010, and the IMAP PST filse were imported using the MailboxImportRequest feature. 
I suspect this is related because of other issues that happen for these accounts.  For instance, all new e-mail was only visible in OWA and not Outlook on all folders on these accounts, and I have had to have the users reset filters in the view settings
for each folder individually.  I don't remember exactly which filter was somehow imported, but it definitely had to do with IMAP.  This may be another red herring, but the behavior is consistent with it.  I should also note that this behavior
did NOT exist when they were connected via IMAP to the old (non MS) server.  I should also note that the filter behavior is somehow stored on the server (and therefore I imagine the delete button behavior could be as well), because creating a new Windows
Profile  (and as such, a new Outlook profile and OST file) on a new computer did not make the IMAP filters go away.