Change the https default port to other port

[RP zim]

I installed zimbra with disabling HTTP and enabling HTTPS port. now it is on production environment. now i want to change the HTTPS port to another port for web client. how do i do that?

another question is that how do I change the custom subject for auto reply out of office ?

My zimbra version is 7.1.3 GA and installed on CENTOS 5.5

[Jignesh]

You can do that with zimbraMailMode.