I need help creating a particular rule.
I get many SPAM emails that contain no text at all. Instead it is a graphic
type that displays text. It looks like "Plain Text" but it is really a
photo embedded into an email. How can I write a rule that will prevent this
type of SPAM. You can't search the body for text. It is worthless trying
to write something that can spot the issue in the header because it can vary
so much.

Any way to write a rule that can detect the absent of all text?