Windows Messenger Connect Invitation API Html Formatted Body

Is there any way to send HTML formatted message body using Windows开发者_高级运维 Messenger Connect Invitation API?

I've many tests but I can send only plain texted messages.

http://msdn.microsoft.com/en-us/library/gg430657.aspx

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It's plain text only. :(

http://social.msdn.microsoft.com/Forums/en/messengerconnect/thread/b9d83e56-940c-47aa-a523-01605c1e169d