SOAP is a standardized XML-based RPC mechanism. It's the mechanism by which the AJAX client communicates with the Zimbra server. To get a sense of what a SOAP request looks like, turn on the AJAX client's debug window (search the forums for details on how to do this) and do something in the client -- fetch a message, mark a message as read, move a contact to the Trash.
SOAP messages are sent to the SOAP servlet on the Zimbra server. I believe that the URL you want to send your SOAP requests to is
http://example.com/service/soap . You should be able to find a SOAP library in the programming language of your choice to expedite this.
The AJAX client explcitly asks for a JSON response because it's a JavaScript app and that's much easier for it to handle. You probably don't want to do this. Make sure that you
don't include the
<format type="js"/> element in the SOAP header.