[FATAL] [unknown] FatalMisconfigurationException: Backend provider 'BackendIMAP' can not be loaded. Check configuration! - code: 0

[switchgott]

Hi,

i tried to install z-push on my openwrt router with NGINX and dovecot.
The Backend i set to BackendImap.
But i get everytime this error:

[FATAL] [unknown] FatalMisconfigurationException: Backend provider 'BackendIMAP' can not be loaded. Check configuration! - code: 0

This is my config:

/**********************************************************************************

• Default FileStateMachine settings
  */
  define('STATE_DIR', '/mnt/data/www/z-push/state');
• Backend settings
  */
  // The data providers that we are using (see configuration below)
  define('BACKEND_PROVIDER', "BackendIMAP");

NGINX:

server {
listen 443;
server_name mail.example.com;

ssl on;
ssl_certificate      server.crt;
ssl_certificate_key  server.key;


root    /mnt/data/www/z-push;
index   index.php;

# not necessary, but might help
#client_max_body_size 4M;
#client_body_buffer_size 128k;

location / {
        try_files $uri $uri/ index.php;
}

location /Microsoft-Server-ActiveSync {
        rewrite ^(.*)$  /z-push/index.php last;
}

location ~ .php$ {
fastcgi_index index.php;
include fastcgi_params;
#fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
fastcgi_pass 127.0.0.1:1026;
fastcgi_param SCRIPT_FILENAME /mnt/data/www/z-push/$fastcgi_script_name;

    # set these two:
    fastcgi_buffer_size 16k;
    fastcgi_buffers 4 16k;

}

Any idea why it doesnt work?

Big big thanks for help!

bye