We have Outlook 2011 on a MAC. We also have Outlook 2007 on PC's we use SBS 2003 now – but realise we have to move to SBS2010. The issue I face is that our IT team say that they cannot sanction such a move unless the outlook calendar sharing is compatible across the MAC and PC if we upgrade to higher version of the exchange server. Please help. Does anyone have MAC and PC sharing calendars via Outlook ? And what version of the exchange server do you have?