2.2.1 Message-ID

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This protocol extends message-id that is defined in [RFC2822]. In this protocol, the Message-ID header indicates that the Internet message is an alert (1) by beginning with a left angle bracket (<) and the alert GUID. The alert GUID is fixed for all alerts (1) and has the value "3BD50098E401463AA228377848493927".

The syntax of this header is defined as follows by using the Augmented Backus-Naur Form (ABNF), as defined in [RFC5234], syntax, as specified in [RFC2822]:

    alert-message-id =       "Message-ID:" alert-msg-id CRLF
    alert-msg-id     =       [CFWS] "<" alert-guid "-" id-left "@" 
                             id-right ">" [CFWS]
    alert-guid       =       "3BD50098E401463AA228377848493927"
    id-left          =       dot-atom-text / no-fold-quote / obs-id-left
    id-right         =       dot-atom-text / no-fold-literal / 
                             obs-id-right

To show that the Message-ID header in this protocol is an extension of Message-ID in [RFC2822], [RFC2822] section 3.6.4 defines a message-id as follows:

    message-id      =       "Message-ID:" msg-id CRLF
    msg-id          =       [CFWS] "<" id-left "@" id-right ">" [CFWS]
    id-left         =       dot-atom-text / no-fold-quote / obs-id-left
    id-right        =       dot-atom-text / no-fold-literal / 
                            obs-id-right

Based on the preceding definitions of alert-message-id and message-id, if alert-guid is considered as a portion of id-left, an alert (1), represented by alert-message-id, conforms to the definition of message-id.

The Message-ID header MUST be present. If alert-message-id as defined earlier is present in Message-ID, the protocol client considers the Internet message as an ALERT and processes the additional alert metadata in the headers as defined in X-AlertId (section 2.2.2) through X-Sharing-Title (section 2.2.11).