Sorry, but Kodak mailer processing was discontinued on 12/31/2009, after Qualex (who ran the mailer program) shut down. Also, processing for EM-26 films by Kodak was discontinued around 2003.
There are still two labs that I know of that still process EM-26 film. One is Film Rescue International in Canada (filmrescue.org), and the other is Plattsburgh Photographic Services (no website, email at super8mm[_at_]aol.com). I don't know what the cost is, but you will probably be better off buying a fresh roll of Ektachrome 100D and processing via Dwayne's Photo.