Contacts are not send in a valid RFC 2426 format?
I use DAVdroid/0.4.3-alpha and a DAViCal server.
I create a new contact on my phone (Galaxy Note 2 using Android 4.1.2)
After the sync I can't see the new contact on Apple Contacts sync with my DAViCal server.
If I use carddavmate http://www.inf-it.com/open-source/clients/carddavmate/ I get an error: "Error: this contact (vCard) is not compliant with RFC 2426!"
Indeed. Please see issue #67 for further discussion.
Maybe it would be nice to indicate on the web site that davdroid is limited to VCard 4.0 support only (for now) and will not work with VCard 3.0 servers like DAViCal.
It would save you some time reading and closing bugs about this known limitation.