+Adding @code{"image/.*"} might also be useful. Spammers use it as the
+prefered part of @samp{multipart/alternative} messages, and you might
+not notice there are other parts. See also
+@code{gnus-buttonized-mime-types} (@pxref{MIME Commands, ,MIME Commands,
+gnus, Gnus Manual}), to which adding @code{"multipart/alternative"}
+enables you to choose manually one of two types those mails include.
+For example, you can set those variables like:
+
+@lisp
+(setq gnus-buttonized-mime-types
+ '("multipart/alternative" "multipart/signed")
+ mm-discouraged-alternatives
+ '("text/html" "image/.*"))
+@end lisp
+
+In this case, Gnus will display radio buttons for such a kind of spam
+message as follows:
+
+@example
+1. (*) multipart/alternative ( ) image/gif
+
+2. (*) text/plain ( ) text/html
+@end example
+