The E-file confirmation receipt says: mail it to Nebraska Service Center, PO Box 87373, Lincoln, NE 68501-7131.
But the following seems to point to a new address:
http://www.uscis.gov/portal/site/uscis/menuitem.5af9bb95919f35e66f614176543f6d1a/?vgnextoid=1d17aca797e63110VgnVCM1000004718190aRCRD&vgnextchannel=fe529c7755cb9010VgnVCM10000045f3d6a1RCRD
If your I-485 receipt number begins with "LIN" or "WAC":
USCIS Phoenix Lockbox
U.S. Postal Service (USPS):
USCIS
P.O. Box 21281
Phoenix, AZ 85036
Express mail and courier deliveries:
USCIS
ATTN: AOS
1820 E. Skyharbor Circle S
Suite 100
Phoenix, AZ 85034