Stop Outlook from butchering Intel brand names with autocorrect

I routinely send recommendations to customers and I'm tired of Outlook butchering Intel's brand names.  An i7 processor is NOT an I7 processor, and yes it looks unprofessional when a recommendation goes out with the brand misspelled.  Why can't I add this to Outlook to tell it to ignore it?  It won't allow me on the other corrections tab either.