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    B2B communication protocols

    AS1: secure EDI over email

    AS1 sends EDI documents as secure email messages. It was the first of the EDIINT applicability statements and is still used by some partners. ECOM supports AS1 connections and helps move partners to AS2 or SFTP when they are ready.

    Specification
    IETF RFC 3335 (EDIINT AS1)
    Transport
    Email (SMTP)
    Message security
    S/MIME encryption and signatures
    Receipts
    MDN returned by email
    Talk to an EDI/API Expert
    Where AS1 fitsA hub diagram: long-standing, low-volume and migrating partners send secure email to the ECOM B2B gateway, which handles S/MIME and receipts and passes documents to the ERP, warehouse, finance and other partners.Where AS1 fitsPartners, the ECOM gateway and your systemsAS1 PARTNERSLong-standing partnersLow-volume partnersPartners migratingYOUR SYSTEMSERPWarehouse (WMS)FinanceOther partnersECOM B2B gatewayAS1S/MIME over emailMDN trackingMigration path to AS2
    Where AS1 fitsA hub diagram: long-standing, low-volume and migrating partners send secure email to the ECOM B2B gateway, which handles S/MIME and receipts and passes documents to the ERP, warehouse, finance and other partners.Where AS1 fitsPartners, the ECOM gateway and your systemsAS1 PARTNERSLong-standing partnersLow-volume partnersPartners migratingECOM B2B gatewayAS1S/MIME over emailMDN trackingMigration path toAS2YOUR SYSTEMSERPWarehouse (WMS)FinanceOther partners

    AS1 partners connect by secure email; their documents reach your systems like any others.

    Expand diagram Download SVG

    Overview

    What AS1 is

    AS1 packages a document with S/MIME, encrypting it for the receiver and signing it, and sends it as an email attachment through mail servers. The receiver returns a Message Disposition Notification by email as a receipt.

    It needs only an email server, which made it easy to adopt. But email delivery can be delayed or filtered, and receipts arrive whenever the mail system delivers them, so most partners now prefer AS2 or SFTP.

    Where businesses use it

    • Long-standing partners

      Partners that set up AS1 years ago and have not changed it.

    • Low-volume exchanges

      Occasional documents where a direct HTTP connection is not available.

    • Migration projects

      Moving AS1 partners to AS2 or SFTP.

    How it works

    How an AS1 exchange works

    The sender signs the document, encrypts it with the receiver's certificate and emails it to the receiver's AS1 mailbox. The receiver's software collects the mail, decrypts it, verifies the signature and returns an MDN by email.

    Because email passes through mail servers, the S/MIME layer is what protects the content. TLS between mail servers, where used, protects each hop but is not guaranteed end to end.

    An AS1 message and its receiptA sequence diagram: the sender signs and encrypts the document, sends it by email through mail servers to the receiver, which decrypts and verifies it and returns an MDN by email.An AS1 message and its receiptSecure email, then a receipt by emailSenderMail serversReceiverSign and encrypt (S/MIME)Email with S/MIME attachmentDelivered to AS1 mailboxDecrypt and verifyMDN receipt by email
    An AS1 message and its receiptA sequence diagram: the sender signs and encrypts the document, sends it by email through mail servers to the receiver, which decrypts and verifies it and returns an MDN by email.An AS1 message and its receiptSecure email, then a receipt by emailSenderMail serversReceiverSign and encrypt(S/MIME)Email with S/MIMEattachmentDelivered to AS1 mailboxDecrypt and verifyMDN receipt by email

    S/MIME protects the content end to end; the receipt comes back by email.

    Expand diagram Download SVG

    In depth

    AS1 in practice

    • S/MIME security

      Encryption and signatures work as in AS2; current partners should use AES and SHA-256 rather than legacy algorithms.

    • Email delivery

      Spam filters, size limits and mail delays can affect delivery. Mailboxes used for AS1 are excluded from filtering that would alter messages.

    • Receipts

      MDNs come back by email; missing receipts are tracked and raised as alerts.

    • Certificates

      Signing and encryption certificates are exchanged and renewed like AS2 certificates.

    • When to migrate

      AS2 or SFTP give faster, more predictable delivery. Migration is planned with the partner and tested in parallel.

    In practice

    Example: moving an AS1 partner to AS2

    A partner has sent invoices by AS1 for years and agrees to move to AS2.

    Example: moving an AS1 partner to AS2Five steps to move a partner from AS1 to AS2: agree the plan, set up AS2, test in parallel, switch, and retire the AS1 mailbox.Example: moving an AS1 partner to AS2A practical example, step by step1Agree the planSet AS2 details anda cutover date withthe partner.Step 12Set up AS2Create the AS2profile andexchangecertificates.Step 23Test in parallelSend test files byAS2 while AS1stays live.Step 34SwitchOn the date,production moves toAS2.Step 45Retire AS1The AS1 mailbox isclosed after a quietperiod.Step 5
    Example: moving an AS1 partner to AS2Five steps to move a partner from AS1 to AS2: agree the plan, set up AS2, test in parallel, switch, and retire the AS1 mailbox.Example: moving an AS1 partnerto AS2A practical example, step by step1Agree the planSet AS2 details and a cutover date withthe partner.Step 12Set up AS2Create the AS2 profile and exchangecertificates.Step 23Test in parallelSend test files by AS2 while AS1 stayslive.Step 34SwitchOn the date, production moves to AS2.Step 45Retire AS1The AS1 mailbox is closed after a quietperiod.Step 5

    Running both in parallel during testing means no documents are lost during the move.

    Expand diagram Download SVG

    Connections

    How AS1 connects your business

    • Trading partners

      AS1 partners exchange documents alongside AS2, SFTP and VAN partners.

    • EDI translation

      Decrypted documents go to translation like any other inbound file.

    • ERP

      Documents reach your ERP whichever protocol the partner uses.

    • Monitoring

      Messages and receipts are logged for audit.

    ECOM

    How ECOM supports AS1

    ECOM supports AS1 with dedicated implementation, mapping, communication and support teams, and with specialists who know the industries your partners work in.

    • Implementation team

      Plans the AS1 setup with you, configures it on the gateway and runs the tests with your partners and systems.

    • Mapping team

      Builds and maintains the maps, code conversions and validation rules between partner data and your applications.

    • Communication team

      Sets up and monitors partner connections, certificates, keys and credentials, and coordinates changes with each partner.

    • Support team

      Watches the flows, investigates failed or missing documents, and works the issue through with you and your partner.

    For AS1 in particular

    • AS1 mailbox, certificate and receipt setup for partners that still require it.
    • Planned migrations from AS1 to AS2 or SFTP, with parallel testing.
    • Partner onboarding for AS1: exchanging connection details, testing in both directions and confirming the go-live date with each partner.
    • Monitoring of every connection, with alerts for failed, missing or unacknowledged transfers.

    Frequently asked questions

    What is the difference between AS1 and AS2?

    Both use S/MIME to encrypt and sign documents and MDNs as receipts. AS1 sends them by email; AS2 sends them directly over HTTP or HTTPS, which is faster and more predictable.

    Is AS1 secure?

    With current algorithms, the S/MIME layer protects the content end to end. Its weakness is email delivery: delays, filtering and size limits, not the encryption.

    Should we move AS1 partners to AS2?

    Usually yes, when the partner can support it. ECOM plans and tests the move with the partner.

    Does ECOM still support AS1?

    Yes, for partners that require it.

    Related pages

    Talk to an EDI/API Expert

    Tell us which partners, systems and AS1 requirements you are working with. An ECOM specialist will review them with you and outline the setup, the maps and the tests.

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