I've tested and reproduced a problem that goes like this:
- Jo is a delegate for Steve.
- When Steve gets an invite, Jo receives a copy and accepts (or declines).
- Jo cannot accept or decline on her Mac using Outlook 2011. (HTTP error: -18500 "The Server Could Not Fulfill The Request.)
Here are some bits of information:
- Jo can accept/decline for Steve using Outlook 2010/2013 (PC/MAPI)
- Jo can accept/decline for Steve using OWA.
- Jo can accept/decline for Steve using Apple's mail.app.
- Jo can accept/decline for other users who have set her up as a delegate from Mac/PC/OWA.
- Other users, if set up as a Delegate for Steve, can accept/decline using Outlook 2011.
- Jo used to be able to do this. At some point, Outlook 2011 crashed and demanded Jo rebuild her database (which she did). Thereafter the problem started.
- I've reproduced the problem on different hardware (and, naturally, different Outlook 2011, different database, different Office identity, etc.)
- EWS tests via Microsoft's Exchange Connectivity Tool pass.
The reason I mention Exchange 2010 is that out of all the various ways to connect, I understand that Outlook 2011 uses Exchange Web Services exclusively to interact with the Exchange server. So, this COULD be an issue with EWS or it could be a permissions issue between Jo and Steve. If I had further insight into the HTTP error, I might be able to go in a direction!
Any and all thoughts welcome!