title: PropertyAccessor error
body: <p>I have an Outlook 2007 add-in made in Visual Basic with Visual Studio 2010. I developed this quite a long time ago and it has always worked fine. I detect embedded images using the attachment PropertyAccessor. I now have to go back and make some changes and am running into the following problem. Attempting get the property now gives me the following error (it never did before)
  <code>The property "http://schemas.microsoft.com/mapi/proptag/0x37140003" is unknown or cannot be found.</code> Other properties I can get fine. I have seen other posts with the same error which mention that the PR_ATTACHMENT_HIDDEN property is not set. I don't understand this as the attachment is an ordinary jpg sent by me from another account. If I build the add-in and install in Outlook 2016 it works just fine. What I find strange is that it used to work with no errors. I don't know if it makes any difference but it is running in VirtualBox.<br>
  Any Ideas would be welcome.</p>