I added a calendar to Outlook by using connect to outlook from within a Sharepoint Calendar. It added but will not sync. The error from send / receive in outlook is:
Task 'Sharepoint' reported error (0x80070005): You do not have permisions to view this Sharepoint list (IT - Calendar). Contact the Sharepoint site administrator. HTTP 302.'
I have ruled out permissions. I think this has to do with alternate access mappings.
I have tested this using outlook connected internally and externally and get the same error. We have http redirecting to https for our sharepoint site.
The alt. access mappings are setup so that http://home.domain.com is in the Intranet zone and https://home.domain.com is in the Internet zone.
Lastly we have tmg proxy setup for external access but I don't think that should impact my interna users as they should go right to the Sharepoint server.