Hello
Outlook doesn't support change the password by RPC over https connections. you can refer to below KB.
http://support.microsoft.com/?id=895276
Change your network password by using any one of the following methods that are available in your environment: • Log on through a VPN connection to the network.
• Log on to the Local Area Network (LAN).
• Use the Internet Information Server (IIS) Change Password feature with Outlook Web Access (OWA). For information about how to configure the IIS Change Password feature, see the following article from the Microsoft Knowledge Base