A very brief tech mystery today!

We have not upgraded to Exchange 2010 yet at work and are still on Exchange 2003 (yes, 2003).  That upgrade is scheduled for a little later this year, but until then, I have to continue to support 2003.

I ran into a strange mail flow issue today that ends up being the result of a combination of Exchange 2003 and Outlook 2007 or newer.  One of my users was trying to send an update to a meeting request, but recipients outside of our domain (external SMTP recipients) were getting stuck in the queue.  The additional information in the queue just said "Unable to open the message for delivery."  That clued me in that it wasn't an external SMTP rejection of the message (invalid email address or whatever).  So I did some googling.

It turns out there's actually a known issue for Outlook 2007 or Outlook 2010 (or newer) clients sending meeting updates via Exchange 2003.  It must not happen all the time, because we've had Outlook 2007 deployed for years and never saw this issue before.  In fact, it didn't start happening until a user on Outlook 2010 sent a meeting update.  Maybe it's just coincidence – I'm not really sure.

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