Hello nipun
Let me start with congratulating you with the tinMCE integration, which is a feature I am looking forward to integrating into my personal RC setup.
Secondly I think there are two separate issues here
-- RC isnt properly notified by Tiny Mce that an email body has been composed, when clearly the text is there , seeing your full text came in. unfortunately I donĀ¹t have a direct a solution for this but perhaps this will help you further
-- The Html garbage is caused by incorrect headers I believe html formatted message require a header looking something like this