Admittedly I currently seem to get overwhelmingly sexually oriented spam, but there is also still a steady trickle of science spam. Some of it is simply ridiculous.
Garish colours. Unprofessional layout. Weird grammar. Grandiose claims. They have the whole package.
Again: I can kind of understand how professionally run vanity presses work, but why do these "publishers" expect anybody who is capable of writing a manuscript without trying to eat the keyboard to be stupid enough to submit their paper to them? Does that really work? These e-mails just don't look at all convincing.