Alias or rewrite to get Horde rpc.php to work

[m1nu2]

Hello all,

I'm trying to setup a nginx server on a RaspberryPi to host a Horde
Groupware. The Webinterface is working so far. But I have problems setting
up the Microsoft-Server-ActiveSync URL to sync my Smartphone and Tablet. I
already asked in the IRC channel and posted a question at Serverfault but
did not get an answer yet. I also googled a lot, tried different solutions,
but non of these worked. So I would be really happy if someone could help me
with that. Here are more details (mainly taken from the Serverfault question
located here:
http://serverfault.com/questions/604866/nginx-alias-or-rewrite-for-horde-groupware-activesync-url-does-not-process-the-r
):

The configuration should allow to access the ActiveSync part via the URL
/horde/Microsoft-Server-ActiveSync. The horde webinterface is already
accessible via /horde

My configuration looks like this:

default-ssl.conf:

server {
        listen                  443 ssl;
        ssl                     on;
        ssl_certificate         /opt/nginx/conf/certs/server.crt;
        ssl_certificate_key     /opt/nginx/conf/certs/server.key;
        server_name             example.com;
        index                   index.html index.php;
        root                    /var/www;

        include sites-available/horde.conf;
}


horde.conf:

location /horde {
        rewrite_log on;
        rewrite ^/horde/Microsoft-Server-ActiveSync(.*)$ /horde/rpc.php$1
last;

        try_files $uri $uri/ /rampage.php?$args;

        location ~ \.php$ {
                try_files $uri =404;
                include sites-available/horde.fcgi-php.conf;
        }
}.


horde.fcgi-php.conf:

include fastcgi_params;
fastcgi_split_path_info ^(.+\.php)(/.+)$;
fastcgi_param PATH_INFO $fastcgi_path_info;
fastcgi_param PATH_TRANSLATED $document_root$fastcgi_path_info;
fastcgi_pass unix:/var/run/php5-fpm.sock;
fastcgi_index index.php;
fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;

So why is the rpc.php not correctly working? 
If I understand correctly it tries to establish a basic authentication
process.
Could this be a problem?
Best regards,
m1nu2

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,250907,250907#msg-250907