All my Kodachrome is mailed to Dwayne's in prepaid envelopes. They mount it in Kodak mounts and send it back to me with a Texas return address, but the postmark on the envelope is from Kansas, hence it was mailed directly from Dwayne's to me. If I mail Fuji mailers and Kodak mailers together to Dwayne's, they arrive the same day. The Kodak is in Texas return address envelopes with a Kansas postmark. The Fuji is in Dwayne's return address envelops with a Kansas postmark. Also, I mail Kodak print mailers to Dwayne's, but they really are processed in Texas and send back quite a bit later than the slide film with a Texas postmark...their print service is as crappy as can be, but the slide service is superb!
It makes no sense, but I figured it out...dang Kodak playing with our minds!