I've enabled calendar.debug.log and calendar.debug.log.verbose (not completely comfortable posting the entire debug trace as it contains a bunch of URLs etc). Outgoing XML request: 63c743fb-4f42-49c5-ac68-e19393db0f70/Exchange: Sending: IdOnly Text On the error above, the error is reported between the 'D' and the 'i' of 'DistinguishedPropertySetId' - which makes no sense, nor can I see any issue with the line verbatim either. I don't see the actual reply content in the debug log: 63c743fb-4f42-49c5-ac68-e19393db0f70/Exchange: reply 63c743fb-4f42-49c5-ac68-e19393db0f70/Exchange: reply 63c743fb-4f42-49c5-ac68-e19393db0f70/Exchange: queueRequest