KMail and base64

I receive a lot of spam email with base64 encoded stuff in it. KMail shows that like this: ------=_NextPart_000_00B8_50D07E0A.D6248A04 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: base64 PGZvbnQgY29sb3IgPSAiZmZmZmZmIj4NCm5sZHINCnJtZHlxZg0KSXdtcA0K [etc..] How can I make this visible in KMail? I mean, how can I let KMail decode that stuff. --Kees