I have my email server running very fine. The web access works and all the stuff is great like calendar, mail, address book and so on.
The problem is the Zimbra Desktop. It works in my laptop, in a virtual machine that I have, in a workstation and in my iphone....but doesn't work in the other laptops

and the error is very strange (see attachment)
The attachment means:
"Host
http://********.dyndns.org:81/service/soap/ not found. Test the hosname and network connection."
The weird thing is that I can login with his account in my laptop but he can't login with any account on his.
All setting are right (couse they work for me) and the server is available because we can login via web access.
Any help please
Thanks