I made an entry in Zimbra Wiki yesterday over how to change the default Advanced Client mode to Basic Client mode without user interaction. You can find it here.
Originally Posted by Costa-101
In sort, I was explaining about:
1. Change default Zimbra HTTP port from TCP/80 to TCP/81.
2. Add your own Apache HTTP webserver and provide relevant configuration.
3. Add a first landing URL which next send URL automatically to new Zimbra HTTP port (TCP/81).
I should say it is simple and non-intrusive hack.
Anthony M. Rasat
Technical, Network and Support Division
PT. Jawa Pos National Network
Jakarta - Indonesia