Applicability Statement 1 (AS1) is an early electronic data interchange (EDI) messaging standard that defines how to securely send data over the internet using email protocols. It uses SMTP for transmission and S/MIME for encryption and digital signatures to enable secure, authenticated message delivery. While AS1 lacks some of the advanced features of newer protocols like AS2 or AS4, it still offers a simple and secure option for organizations that require email-based file transfers. In managed file transfer (MFT) workflows, AS1 provides message-level security and verification, including message disposition notifications (MDNs), which confirm delivery and integrity. This makes it useful in scenarios where legacy systems or specific compliance needs mandate continued AS1 support.
Core AS1 features
AS1 combines basic internet protocols with encryption and authentication to facilitate secure EDI communication over email. While less common today, it remains useful for some organizations with legacy systems or limited bandwidth requirements. Some core AS1 features are that it:
- Enables basic B2B file exchange without requiring direct system connections
- Operates efficiently in low-bandwidth or high-latency environments
- Relies on S/MIME for message encryption and digital signatures
- Supports MDNs for receipt verification and non-repudiation
- Uses SMTP for email-based file transport
AS1 provides foundational security and reliability in email-based data exchanges, though many modern MFT environments have transitioned to AS2 or AS4 for added functionality.
How AS1 works
AS1 transmits EDI files as email attachments using SMTP, with each file secured by S/MIME. This ensures confidentiality and integrity through encryption and digital signing. Upon successful receipt, the recipient’s system may return a signed MDN as confirmation. These notifications help confirm message delivery and protect against repudiation claims. Despite its simplicity, AS1 enables secure, traceable exchanges when properly configured, particularly in environments that prioritize email-based communication over more complex protocol stacks.
AS1 advantages
AS1 enables email-based secure file transfers, which can be beneficial in low-resource or legacy environments. Its reliance on SMTP and S/MIME provides a universally compatible method for sending signed and encrypted messages without requiring complex integrations or dedicated VPNs.
Limitations when using AS1
AS1 does not offer real-time capabilities, advanced routing or the enhanced reliability of newer protocols. Email-based transmission can introduce delivery delays, dependency on mail servers and limitations in scalability. These factors make AS1 less suitable for high-volume or latency-sensitive transfers.
AS1 FAQs
What are AS1 and AS2?
AS1 and AS2 help send EDI messages in a secure way. AS1 uses email with SMTP and S/MIME to move files. AS2 uses HTTP or HTTPS to send files directly over the internet. AS2 is faster and handles errors better. This makes it a good choice for systems that move large amounts of data or need low delays.
Both AS1 and AS2 use digital signatures. They also support encryption and message receipts. AS2 is stronger for business use. It supports real-time transfers and works well in complex networks. Many organizations choose it for daily operations.
What is the difference between AS1, AS2 and AS3?
AS1 moves files through email using SMTP and S/MIME. It sends messages from one system to another. AS2 uses HTTP or HTTPS. It supports real-time delivery between two parties. It is known for strong reliability. AS3 works differently. It uses FTP, SFTP or FTPS. It moves files instead of messages. It wraps each file in a set format.
AS1 and AS2 focus on messages. AS3 focuses on files. Each option fits different needs. The best choice depends on the setup. It also depends on rules the organization must follow. AS2 is common because it sends files quickly and directly.
What protocol does EDI use?
EDI uses different transport protocols. These include AS1, AS2, AS3, FTP, SFTP and HTTP/S. The choice depends on the systems already in place. It also depends on what rules the organization needs to follow. AS2 is the most widely used today. It is fast and reliable. It also allows secure transmissions between systems.
Older setups may still rely on AS1 or AS3. These are useful for email or file-based communication. Some businesses still need them. Many MFT tools support all of these protocols. This helps different systems work together without issues.
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