AS1 (Applicability Standard 1) is the RFC standard (RFC3335) that enables vendor applications to communicate EDI or other business-to-business data (such as XML) over the Internet using SMTP, the standard used for email.
AS1 provides security for the transport payload through digital signatures and data encryption and ensures reliable, non-reputable delivery through the use of receipts. AS1 specifies how to create a connection and transport data, not how to validate or process data. Many AS1 applications provide data compression, but this is not an actual part of the specification. AS1 was developed as part of the IETF EDIINT Work Group.
For more information on AS1, please refer to:http://www.ietf.org/rfc/rfc3335.txt