Tim
rpm -qa |grep zarafa output;
app-zarafa-community-1.5.20-1.v6.noarch
zarafa-server-7.1.11-46050.x86_64
app-zarafa-core-1.5.25-1.v6.noarch
zarafa-webapp-1.3.2-42118.noarch
zarafa-spooler-7.1.11-46050.x86_64
app-zarafa-1.5.25-1.v6.noarch
app-zarafa-extension-core-1.2.6-1.v6.noarch
zarafa-common-7.1.11-46050.x86_64
zarafa-monitor-7.1.11-46050.x86_64
zarafa-libs-7.1.11-46050.x86_64
zarafa-dagent-7.1.11-46050.x86_64
zarafa-ical-7.1.11-46050.x86_64
zarafa-search-7.1.11-46050.x86_64
app-zarafa-community-core-1.5.20-1.v6.noarch
zarafa-licensed-7.1.11-46050.x86_64
zarafa-libarchiver-7.1.11-46050.x86_64
zarafa-utils-7.1.11-46050.x86_64
zarafa-contacts-7.1.11-46050.x86_64
zarafa-webaccess-7.1.11-46050.noarch
zarafa-7.1.11-46050.x86_64
zarafa-z-push-2.2.0-1.v6.noarch
zarafa-client-7.1.11-46050.x86_64
zarafa-gateway-7.1.11-46050.x86_64

You are correct about the message being from Firefox. I get the same result with IE or Chromium.
I am able to successfully log onto Webapp, using the same URL, whilst inside my network.