The connector is sold with OpenXchange on their web site.
I also tried Toltec and Insight connectors with a cyrus-imap running on SME6.0. This was a great solution. But now, with SME7, nothing does it. DevTeam seems to stick to dovecot and to keed away from cyrus-imap.
The openXchange approach is complicated compared to cyrus-imap. I had OX running and then broke it whithout knowing which modification could have caused the problem. It sits there out of order.
The only way I know to keep it simple is to install basic CENTOS with Kolab. But this drives me away from the help from the community and from SME. As I'm no guru and don't want to become one, Kolab is the best shot, but support is poor.
Another way is with EGroupware. When php5 will be available on SME7, EGW will sync with open source connectors. In the mean time, a box with CENTOS and PHP5 would let you sync.
Many threads about this kind of need never triggered any developer's interest even if the need is real.