The P90X specific newsletter began in 2009 and we've got an indexed archive up on my site:
P90X Newsletter Archive
It's not too differenent from the normal Beachbody Newsletter except the content is often geared more towards graduate-level workout programs instead of any workout program. Topics may include anything about nutrition or fitness but you'll also find targets subjects customizing P90X, how to create hydrid programs with Insanity, Turbo Fire, 90X and any of our graduate programs, a how to use our workouts for sports specific training. If you don't find a subject you're looking for don't forget to look on our standard archive, which goes all the way back to 2000.
Beachbody Newsletter Archive