From the e-mail ...
Offer: Purchase and fly round trip on nonstop Delta flights between LAX and RDU, BDL, JAX, CMH, MSY, BOS, JFK, MCO, FLL, and CVG between October 8 and December 7, 2007 and earn double MQMs for each round trip. Bonus applies only to Medallion Qualification Miles.
Seems to me that not only would your SLC-LAX-JFK not apply, but your trip would need to originate in LAX, as well? (In other words, a JFK-LAX-JFK would not apply?)