From the US Postal Service:
Louisiana: As Hurricane Isaac approaches the Gulf Coast, Louisiana District is requesting mailers to divert drop shipment mail for the following facilities listed:
All drop shipments mail destined to New Orleans LA P&DC 700 ZIP Codes: 700-701, 703-704 will be accepted at Shreveport LA P&DC 710 until further notice.
All drop shipments mail destined to Baton Rouge LA P&DC 707 ZIP Codes: 705-708 will be accepted at Lafayette LA P&DC 705 until further notice.
For more updates visit usps.com: Mail Service Updates.