MXP (MUD eXtension Protocol) is a protocol made by Zuggsoft for use with ZMud client (mainly).
http://www.zuggsoft.com/zmud/mxp.htmThe reason we do not support this protocol by default is that it is in our view bloated with unnecessary output and harder to implement server side than SFXP. We do not want to base the core protocol used in ScapeFX on something developed and maintained by another mud client company. It would leave the protocol spec out of our control. With our own protocol we can more easily control what is going to be added or removed and we can integrate it easier with the client.
HOWEVER, for muds that really do want to use MXP instead of SFXP it is not hard to add a ScapeFXAPI_NetworkParser written for MXP to replace the default SFXP parser. When time allows we will also write this plugin as a sample plugin on the wiki.