IRS expanded the list of Private delivery services (if you don't opt for the U.S.P.S.) you can use to satisfy its "timely mailing as timely filing/paying" rule.  They are:

• Airborn Express -Overnight Air Express Service, Next Afternoon Service and Second Day Service.
• DHL Worldwide Express (DHL) - DHL Same Day Service and DHL USA Overnight.
• Federal Express (FEDEX) - FedEx Priority Overnight, Fed Ex Standard Overnight, and FedEx 2nd Day
• United Parcel Service (UPS) - UPS Next Day Air, UPS Next Day AirSaver, UPS 2nd Day Air, UPS 2nd Day Air A.M., UPS Worldwide Express Plus and UPS Worldwide Express.

EFFECTIVE SEPTEMBER 1, 2001