Howto use "addPrefix"?

Traefik Traefik v2 (latest)
,
1

Situation: Our SLES12 server (https://local-IP/) provides

  • under "/" a normal Welcome Page (apache 2.4)
  • under "/gw/webacc" a GroupWise Webmail application (served by tomcat)

our current reverse proxy (apache 2.4) is setup to handle calls to

https://server.my-domain.de/ by    ProxyPass "/" "https://server.oes.ml-bw.de/"

https://mail.my-domain.de/ by      RewriteRule ([^/]*)(.*) https://server.hhs-aalen.de/gw/webacc$2

I tried to use

      entryPoints:
        - websecure
      rule: "Host(`mail.my-domain.de`)"
      service: mobil-service
      middlewares:
         - mobil-prefix
      tls:
        options: withsni
        certResolver: letsencrypt

  services:
    mobil-service:
      loadBalancer:
        servers:
          - url: "https://192.168.1.2/"

  middlewares:
    mobil-prefix:
      addPrefix:
        prefix: "/gw/webacc"

calling "https://mail.my-domain.de" gives me an blank screen and the debugger shows

<form name="loginForm" method="post" action="/gw/webacc" class="gray_bg_5" style="visibility: hidden">

direct call to "https://server.my-domain.de/gw/webacc" gives a login window and

<form name="loginForm" method="post" action="/gw/webacc" class="gray_bg_5" style="visibility: visible">

See the difference in "visibility"

I also tried to use "redirectRegex" but don't know howto use this to simulate the above mentioned apache rewrite syntax.