I'm a mailman and this is straight from USPS News Link (for postal employees):

"Now it can be Scent

New option for mailing DOT-approved shipments

Heightened concerns about security and safety in recent years have meant that most mailings containing cosmetics must be sent by surface transportation — until now. The Postal Service has revised mailing standards in the Domestic Mail Manual to allow shippers to send beauty aids by air.

Shippers have to obtain a U.S. Department of Transportation (DOT) Special Permit 9275, and the parcels have to be packed according to safety control measures. Mailers who qualify may now use First-Class Mail, Priority Mail or Parcel Select service for their goods. Parcels sent with the permit must have a label on the address side of the package that reads “USPS Approved DOT – SP 9275.”

“Shippers of beauty aids are delighted to have these options for timely delivery of their products,” said USPS Manager of Mailing Standards Sharon Daniel.

Cambridge, MA-based beauty products giant Crabtree & Evelyn also is enthusiastic about the change. “We knew we could achieve results that other businesses could benefit from by joining as partners with the USPS team,” said Donna Young, the company’s U.S. distribution director.

Click here for more information about the mailing standards that govern SP 9275. Scroll to 601.10.13.5." (Sorry but no clicking allowed. It bascially points to a document called the Domestic Mail Manual (DMM))

John