receiving HTML messages in KMail

I am running KMail 1.9.10 in KDE 3.5.10, which is standard in Slackware 12.2.  
(I hear that the next release of Slackware will have KDE 4.*.)

I see in the KMail Handbook under 3. "Using KMail" there is a 
section "Creating HTML Messages".  However, I can't find the instructions on 
how to *read* an HTML message that I have received.  When I get an HTML 
message, I can see the HTML source code in the Message Preview Panel of the 
Main Window of KMail, but where does it tell you how to invoke the HTML 
interpreter on the source code?

Thanks & Best Regards,
Lou
New York City