Roundcube - Nginx不会自动重定向到.php文件

EDITED!

I set up a mail server on Debian 7 with Nginx, Postfix, Postfixadmin, Dovecot and Roundcube.

I tried to create an alias to use the SSL certificate of my domain example.org (of course, the domain here is an example) for the webmail. When accessing the following URL https://example.org/support/webmail/ - Nginx doesn't redirect to the index.php file and I get the following message 403 Forbidden. It only works if I manually add a .php file at the end of the URL.

Here's my configuration:

server {
    listen 80;
    server_name example.org;
    return 301 https://$server_name$request_uri;
}

server {
    listen 80;
    server_name www.example.org;
    return 301 https://$server_name$request_uri;
}

server {
    listen 443 ssl;
    ssl on;

    server_name example.org;
    root /var/www/soon;

    server_tokens off;

    ssl_certificate /etc/ssl/certs/example.org.certchain.crt;
    ssl_certificate_key /etc/ssl/private/example.org.key;

    ssl_session_cache shared:SSL:20m;
    ssl_session_timeout 10m;

    ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
    ssl_ciphers ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-SHA384:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256;
    ssl_prefer_server_ciphers on;

    # HSTS
    add_header Strict-Transport-Security max-age=15768000;

    location /support/webmail/ {
        alias /var/www/webmail/;
        autoindex off;

        location ~ \.php$ {
          include       /etc/nginx/fastcgi_params;
          # include       fastcgi_params;
          fastcgi_pass  unix:/var/run/php5-fpm.sock;
          fastcgi_index index.php;
          # fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
          fastcgi_param SCRIPT_FILENAME $request_filename;
        }
    }
}

Thank you. :)