X-Lite 4.7 apparently sends IM material as text/html. This creates interoperation problems with some other SIP clients. I get this kind of responses: SIP/2.0 415 Unsupported Media Type. All UAs that support the SIP MESSAGE method must support plain/text format. I need help!
This is a question for Counterpath, although they probably will not answer it as X-Lite will probably be provided on a free of charge but unsupported basis.
Counterpath answerd: “You will need to get the PBX or far end client to support the media type that X-Lite sends it in.”
Then use a standards compliant phone, instead.