CSX does handle Springfield BMC intermodal traffic as evidenced by the UMAX boxes. Much of it may not be for the account of the US Postal Service per se, but, there is 3rd class mail that once had been USPS traffic that now moves via other carriers due to postal rate incentives for its customers to purchase their own transportation to tender mail as deeply into the USPS's distribution network as possible. So, CSX is handling magazines and direct mail pieces (eg. catalogs, coupon packs, etc.), possibly some parcels, for the accounts of Schneider, Hunt, Hub City, etc., quite possibly for the direct-mailers themselves, which will be entered into the USPS distribution stream at the Springfield BMC or other area facilities. Very likely they handle postal equipment also (pallets, bags, racks, etc.) and some 3rd or 4th class mail. The West Springfield intermodal terminal has a long history of handling traffic associated with the Springfield BMC. Amtrak, despite success in soliciting traffic, chose to exit the mail handling business when David Gunn served as their president. FedEx, on the other hand, is a relative newcomer to intermodal and most likely that FedEx move at WSP was related to their own traffic and not with the USPS.