I've been struggling with this for a while now and here is a workaround that actually works when using Nginx. You must add the following rewrite rule in nginx deafult.conf under the "server" block:
rewrite ^/.well-known/carddav /SOGo/dav permanent;
After the line is added, restart nginx and it should work immediately.
Strange that this issue is not resolved from Apple yet. The bug still exists in 10.11.2 beta.
/Daniel
