Apache Document root auf anderen lokalen Webserver umleiten

<VirtualHost *:80>
        ServerName mail.example.com
        RewriteEngine On
        RewriteRule ^/.* https://mail.example.com/SOGo
        #Redirect permanent / https:{{comment_single_line_double_slash:0}}
</VirtualHost>

<IfModule mod_ssl.c>
<VirtualHost *:443>
       ServerName mail.example.com
       DocumentRoot /var/www/vsites/mail.example.com
       Header always set Strict-Transport-Security "max-age=63072000; includeSubDomains; preload"  

       RewriteEngine On
       RewriteRule ^/$ https://mail.example.com/SOGo
       ErrorLog ${APACHE_LOG_DIR}/error.log

        # Possible values include: debug, info, notice, warn, error, crit,
        # alert, emerg.
        LogLevel warn

        CustomLog ${APACHE_LOG_DIR}/ssl_access.log combined

        #   SSL Engine Switch:
        #   Enable/Disable SSL for this virtual host.
        SSLEngine on

        #   A self-signed (snakeoil) certificate can be created by installing
        #   the ssl-cert package. See
        #   /usr/share/doc/apache2.2-common/README.Debian.gz for more info.
        #   If both key and certificate are stored in the same file, only the
        #   SSLCertificateFile directive is needed.
        SSLCertificateFile    /etc/letsencrypt/live/mail.example.com-0001/fullchain.pem
        SSLCertificateKeyFile /etc/letsencrypt/live/mail.example.com-0001/privkey.pem

Alias /SOGo.woa/WebServerResources/ \
      /usr/lib/GNUstep/SOGo/WebServerResources/
Alias /SOGo/WebServerResources/ \
      /usr/lib/GNUstep/SOGo/WebServerResources/

<Directory /usr/lib/GNUstep/SOGo/>
    AllowOverride None

    <IfVersion < 2.4>
        Order deny,allow
        Allow from all
    </IfVersion>
    <IfVersion >= 2.4>
        Require all granted
    </IfVersion>

    # Explicitly allow caching of static content to avoid browser specific behavior.
    # A resource's URL MUST change in order to have the client load the new version. 
    <IfModule expires_module>
      ExpiresActive On
      ExpiresDefault "access plus 1 year"  
    </IfModule>
</Directory>

## Uncomment the following to enable proxy-side authentication, you will then
## need to set the "SOGoTrustProxyAuthentication" SOGo user default to YES and 
## adjust the "x-webobjects-remote-user" proxy header in the "Proxy" section 
## below.
#
## For full proxy-side authentication:
#<Location /SOGo>
#  AuthType XXX
#  Require valid-user
#  SetEnv proxy-nokeepalive 1
#  Allow from all
#</Location>
#
## For proxy-side authentication only for CardDAV and GroupDAV from external
## clients:
#<Location /SOGo/dav>
#  AuthType XXX
#  Require valid-user
#  SetEnv proxy-nokeepalive 1
#  Allow from all
#</Location>

ProxyRequests Off
SetEnv proxy-nokeepalive 1
ProxyPreserveHost On

# When using CAS, you should uncomment this and install cas-proxy-validate.py
# in /usr/lib/cgi-bin to reduce server overloading
#
# ProxyPass /SOGo/casProxy http://localhost/cgi-bin/cas-proxy-validate.py
# <Proxy http://localhost/app/cas-proxy-validate.py>
#   Order deny,allow
#   Allow from your-cas-host-addr
# </Proxy>
ProxyPass /SOGo http://127.0.0.1:20000/SOGo retry=0

# Enable to use Microsoft ActiveSync support
# Note that you MUST have many sogod workers to use ActiveSync.
# See the SOGo Installation and Configuration guide for more details.
#
ProxyPass /Microsoft-Server-ActiveSync \
 http://127.0.0.1:20000/SOGo/Microsoft-Server-ActiveSync \
 retry=60 connectiontimeout=5 timeout=360

<Proxy http://127.0.0.1:20000/SOGo>
## adjust the following to your configuration
  RequestHeader set "x-webobjects-server-port" "443"  
  RequestHeader set "x-webobjects-server-name" "example.com"  
  RequestHeader set "x-webobjects-server-url" "https://mail.example.com"  

## When using proxy-side autentication, you need to uncomment and
## adjust the following line:
  RequestHeader unset "x-webobjects-remote-user"  
#  RequestHeader set "x-webobjects-remote-user" "%{REMOTE_USER}e" env=REMOTE_USER  

  RequestHeader set "x-webobjects-server-protocol" "HTTP/1.0"  

  AddDefaultCharset UTF-8

  Order allow,deny
  Allow from all
</Proxy>

# For Apple autoconfiguration
<IfModule rewrite_module>
  RewriteEngine On
  RewriteRule ^/.well-known/caldav/?$ /SOGo/dav [R=301]
  RewriteRule ^/.well-known/carddav/?$ /SOGo/dav [R=301]
</IfModule>

        BrowserMatch "MSIE [2-6]" \  
                nokeepalive ssl-unclean-shutdown \
                downgrade-1.0 force-response-1.0
        # MSIE 7 and newer should be able to use keepalive
        BrowserMatch "MSIE [17-9]" ssl-unclean-shutdown  

</VirtualHost>
</IfModule>