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Thunderbird 31/Lightning 3.3 is only sending new appointments. It does not receive new ones.
Same issue with sync from Android device, via CalDAV-Sync 0.4.16 helper application.
Which brings me to suspect SM is at fault.
SM version is 12.1.5224 Enterprise
Release notes up to latest version 12.4.5364 make no mention of calDAV fixes, so haven't installed it yet.
Outlook 2007 (via Sharepoint lists) is sync'ing both ways.
This is the first time I've attempted to use calDAV with SM, so it could even be some setting that I'm missing...?