Why don't Exchange Calendar invites automatically delete the associated email anymore

On my iPhone 4, running IOS 5, when I accepted an MS Exchange 2008 meeting request from the iPhone calendar app, it would automatically delete the associated meeting request e-mail in my MS Exchange inbox. Since upgrading to an iPhone 5 and IOS 6.01, it does not delete the meeting request e-mail. This consistently happens with every meeting request. I have tried everything I can think of. Completely resetting my iPhone, reloading the firmware, deleting all e-mail accounts and adding them again. Tried countless different settings, but the problem still persists. Nothing has changed on the Exchange server, the only thing that's different is IOS 6. I've seen this problem mentioned on several other forums, but no one has an answer. If I could get at some logs, I might be able to provide some debugging info, but I'm not sure where to find them.

Anyone else have this problem? Did you resolve it? If so, what is the magic required to fix it?

TIA,

Doug