I can only salute USCIS for its decision to set up a special filing location at the California Service Center; sometimes, no matter how you flag an application, the folks in the mail room miss the fact that the application has been properly filed.

For Direct Mail:
U. S. Citizenship and Immigration Services
California Service Center
ATTN: CAP EXEMPT H-1B Processing Unit
P.O. BOX 30040
Laguna Niguel, CA 92607-3004

For non-United States Postal Service (USPS) deliveries (e.g. private couriers):
U. S. Citizenship and Immigration Services
California Service Center
ATTN: CAP EXEMPT H-1B Processing Unit
24000 Avila Road, Room 2312
Laguna Niguel, CA 92677

Each H-1B petitioner is encouraged to mark the outside of the envelope and the top margin of the I-129 form, with “EXEMPT.” This will ensure quick identification of the H-1B filing throughout the petition’s processing at CSC.

Link to update, “USCIS ANNOUNCES CENTRALIZED FILING LOCATION FOR CERTAIN H-1B CAP EXEMPT PETITIONERS“