I tried to play around with Outlook 2003 and GPO. I thought to disable the outlook 2003 option 'Remove extra line breaks in plain text messages' for the client systems. I thought to do this whether we can try with any registry setting or GPO?

Later i done the same with GPO like this.

In Outlook 2003, it's:
PART "Automatically clean up plain text messages" CHECKBOX
KEYNAME Software\Policies\Microsoft\Office\11.0\Outlook\Options\Mail
VALUENAME AutoFormatPlainText
VALUEON NUMERIC 1
VALUEOFF NUMERIC 0


Also you can refer the KB: http://support.microsoft.com/default.aspx/kb/287816