(Visual FoxPro) Processing a multipart/report Delivery Status Notification (Bounce Notification)

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This example discusses the format of Delivery Status Notification emails and how to process them.

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LOCAL lnSuccess
LOCAL loEmail
LOCAL loH2t
LOCAL loSa
LOCAL lnNumFinalRecipients
LOCAL i
LOCAL lcHeadersText
LOCAL loMime
LOCAL loOrigEmail

* Here are the MIME structures, showing the content-type and nesting of the MIME parts of three sample
* multipart/report DSN (Delivery Status Notification) emails.

* This 1st sample includes a "text/rfc822-headers" MIME subpart. 

* multipart/report
*     text/plain
*     message/delivery-status
*     text/rfc822-headers
*     message/rfc822

* This 2nd sample lacks the text/rfc-headers part, but the "report type" information
* is offered in both plain-text and HTML formats.

* multipart/report
*     multipart/alternative
*         text/plain
*         text/html
*     message/delivery-status
*     message/rfc822

* ----------------------------------------------------------------------------------------------------

* A multipart/report MIME delivery status notification follows a specific format defined by the Internet Engineering Task Force (IETF) in RFC 3464, 
* which outlines the "An Extensible Message Format for Delivery Status Notifications" standard. The format consists of multiple parts within a 
* multipart/report structure. Here's an overview of the main parts involved:
* 
* The 1st sub-part under multipart/report is the body of the DSN to be displayed by the email client (such as Outlook).
* It can be a simple text/plain body, or it can be multipart/alternative and offer a few alternative format, typically plain-text and HTML.
* HTML is best for viewing a program such as Outlook. 
* This part of the multipart/report is not structured for programmatic processing.  It's meant to be viewed by a human.

* --------------------
* The "message/delivery-status" part within a multipart/report MIME structure follows a specific format to provide details about the delivery status
* of an email message.  Here's an overview of the format and the key components within the "message/delivery-status" part:
* 
* (1) Content-Type and Reporting-UA:
* The "message/delivery-status" part begins with the Content-Type header specifying "message/delivery-status". 
* It may also include a Reporting-UA (Reporting User Agent) field that identifies the software or system generating the delivery status notification.
* 
* For example:
* 
* Content-Type: message/delivery-status
* Reporting-UA: Example Mail System 1.0
* 
* (2) Fields:
* The "message/delivery-status" part contains a series of fields, each providing specific information about the delivery status. 
* These fields are structured as key-value pairs.
* 
* Common fields include:
* 
*     Final-Recipient: Specifies the recipient for whom the delivery status is being reported.
*     Action: Describes the action performed by the reporting system (e.g., failed, delivered, delayed, etc.).
*     Status: Indicates the status code or reason for the delivery attempt result.
*     Remote-MTA: Specifies the host or system that attempted the delivery.
*     Diagnostic-Code: Provides additional diagnostic information, such as error codes or explanations.
* 
* For example:
* 
* Final-Recipient: rfc822; john.doe@example.com
* Action: failed
* Status: 5.1.1
* Remote-MTA: smtp.example.com
* Diagnostic-Code: smtp; 550 Requested action not taken: mailbox unavailable
* 
* (3) Additional Fields:
* Additional fields may be included in the "message/delivery-status" part to provide further information about the delivery attempt. 
* These fields can vary depending on the implementation or specific needs of the system generating the delivery status notification.
* For example:
* 
* X-Spam-Flag: YES
* X-Spam-Score: 7.2
* 
* Note: The specific fields and their values within the "message/delivery-status" part can vary depending on the implementation
* or the email server/application generating the delivery status notification. The structure described above represents the standard format
* as defined in RFC 3464, but variations may exist in practice.

* --------------------

* The "text/rfc822-headers" MIME part, if included, contains the headers of the original email message
* for which the delivery status notification is being generated. It provides a subset of the headers from the original message,
* typically excluding the message body and attachments.
* 
* The purpose of including the "text/rfc822-headers" part is to provide contextual information about the original message.
* It allows the recipient to review the original headers, such as the subject, sender, recipients, date, and other relevant information,
* in order to understand the context and details of the email message for which the delivery status notification is being generated.
* 
* Note that the specific headers included in the "text/rfc822-headers" part can vary based on the implementation or requirements
* of the system generating the delivery status notification.

* --------------------

* If the message/rfc822 part is present, it contains the full MIME of the email that was not delivered.
* In Chilkat terminology, this is an attached message.

* OK, let's write code to process a multipart/report email.

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.Email')
loEmail = CreateObject('Chilkat.Email')
lnSuccess = loEmail.LoadEml("qa_data/eml/deliveryStatus.eml")
* success = email.LoadEml("qa_data/eml/sample_multipart_report.eml");
IF (lnSuccess = 0) THEN
    ? loEmail.LastErrorText
    RELEASE loEmail
    CANCEL
ENDIF

* Verify this is a multipart/report email..
IF (loEmail.IsMultipartReport() = 0) THEN
    ? "Not a multipart/report email."
    RELEASE loEmail
    CANCEL
ENDIF

* Get the body that is to be displayed to a human in an email program (such as Outlook).
IF (loEmail.HasPlainTextBody() = 1) THEN
    ? "Plain text body:"
    * println email.GetPlainTextBody();
ELSE
    IF (loEmail.HasHtmlBody() = 1) THEN
        * Convert HTML to plain-text..
        * For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.HtmlToText')
        loH2t = CreateObject('Chilkat.HtmlToText')
        ? "HTML body converted to plain-text:"
        ? loH2t.ToText(loEmail.GetHtmlBody())
    ELSE
        ? "Has no plain-text or HTML body..."
    ENDIF

ENDIF

? "---------------------------------"

* Now get information from the message/delivery-status part (or the message/disposition-notification part)
? "--- Delivery Status Information:"
? "Status: " + loEmail.GetDeliveryStatusInfo("Status")
? "Action: " + loEmail.GetDeliveryStatusInfo("Action")
? "Reporting-MTA: " + loEmail.GetDeliveryStatusInfo("Reporting-MTA")

loSa = loEmail.GetDsnFinalRecipients()
lnNumFinalRecipients = loSa.Count
i = 0
DO WHILE i < lnNumFinalRecipients
    ? "final recipient: " + loSa.GetString(i)
    i = i + 1
ENDDO
RELEASE loSa

? "---------------------------------"

* If the multipart/report contains a text/rfc822-headers, it can be retrieved like this:
lcHeadersText = loEmail.GetNthTextPartOfType(0,"text/rfc822-headers",0,0)
IF (loEmail.LastMethodSuccess = 1) THEN
    ? "The text/rfc822-headers part exists.."
    ? ""
    ? lcHeadersText

    * If you wish to process the headers, you can load them into a MIME object and use the Chilkat MIME functionality to examine the headers.
    * For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.Mime')
    loMime = CreateObject('Chilkat.Mime')
    loMime.LoadMime(lcHeadersText)

    * Do whatever you want.. 
    * For example, look at the "To" header.
    ? "MIME To header:"
    ? loMime.GetHeaderField("To")
ENDIF

? "---------------------------------"

* Finally, if the original email was attached, you can load it into another Chilkat Email object instance and
* do what you want with it..

IF (loEmail.NumAttachedMessages > 0) THEN
    * Get the 1st attachment message (assume we don't have more than one attached message)
    loOrigEmail = loEmail.GetAttachedMessage(0)
    IF (loEmail.LastMethodSuccess = 1) THEN
        ? "Attached message subject: " + loOrigEmail.Subject
        * Do whatever else you want..
        RELEASE loOrigEmail
    ENDIF

ENDIF

RELEASE loEmail
RELEASE loH2t
RELEASE loMime