I'm running the italian version so I'm in troubles in giving you the exact path to follow, but is almost like:
Administrator -> Config -> Domains -> (domainname) -> [General information] : "Hostname for the public service"
and set your domain name without your hostname, should work.
I paste you some info I've found dime ago probably in this forum:
Setting up a Public Service Host Name
You can configure each domain with the public service host name to be used for REST URLs. This is the URL that is used when sharing Documents Notebooks, email folders and Briefcase folders, as well as sharing task lists, address books, and calendars.
When users share a ZCS folder, the default is to create the URL with the Zimbra server hostname and the Zimbra service host name. This is displayed as
http://server.domain.com/service/hom...e/sharedfolder. The attributes are generated as follows:
* Hostname is server.zimbraServiceHostname
* Protocol is determined from server.zimbraMailMode
* Port is computed from the protocol
When you configure a public service host name, this name is used instead of the server/service name, as
http://publicservicename.domain.com/...e/sharedfolder. The attributes to be used are:
* zimbraPublicServiceHostname
* zimbraPublicServiceProtocol
* zimbraPublicServicePort
You can use another FQDN as long as the name has a proper DNS entry to point at ‘server’ both internally and externally.
Regards