(Ruby) 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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require 'chilkat'

# 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.

email = Chilkat::CkEmail.new()
success = email.LoadEml("qa_data/eml/deliveryStatus.eml")
# success = email.LoadEml("qa_data/eml/sample_multipart_report.eml");
if (success == false)
    print email.lastErrorText() + "\n";
    exit
end

# Verify this is a multipart/report email..
if (email.IsMultipartReport() == false)
    print "Not a multipart/report email." + "\n";
    exit
end

# Get the body that is to be displayed to a human in an email program (such as Outlook).
if (email.HasPlainTextBody() == true)
    print "Plain text body:" + "\n";
    # println email.GetPlainTextBody();
else
    if (email.HasHtmlBody() == true)
        # Convert HTML to plain-text..
        h2t = Chilkat::CkHtmlToText.new()
        print "HTML body converted to plain-text:" + "\n";
        print h2t.toText(email.getHtmlBody()) + "\n";
    else
        print "Has no plain-text or HTML body..." + "\n";
    end

end

print "---------------------------------" + "\n";

# Now get information from the message/delivery-status part (or the message/disposition-notification part)
print "--- Delivery Status Information:" + "\n";
print "Status: " + email.getDeliveryStatusInfo("Status") + "\n";
print "Action: " + email.getDeliveryStatusInfo("Action") + "\n";
print "Reporting-MTA: " + email.getDeliveryStatusInfo("Reporting-MTA") + "\n";

# sa is a CkStringArray
sa = email.GetDsnFinalRecipients()
numFinalRecipients = sa.get_Count()
i = 0
while i < numFinalRecipients
    print "final recipient: " + sa.getString(i) + "\n";
    i = i + 1
end

print "---------------------------------" + "\n";

# If the multipart/report contains a text/rfc822-headers, it can be retrieved like this:
headersText = email.getNthTextPartOfType(0,"text/rfc822-headers",false,false)
if (email.get_LastMethodSuccess() == true)
    print "The text/rfc822-headers part exists.." + "\n";
    print "" + "\n";
    print headersText + "\n";

    # 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.
    mime = Chilkat::CkMime.new()
    mime.LoadMime(headersText)

    # Do whatever you want.. 
    # For example, look at the "To" header.
    print "MIME To header:" + "\n";
    print mime.getHeaderField("To") + "\n";
end

print "---------------------------------" + "\n";

# 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 (email.get_NumAttachedMessages() > 0)
    # Get the 1st attachment message (assume we don't have more than one attached message)
    # origEmail is a CkEmail
    origEmail = email.GetAttachedMessage(0)
    if (email.get_LastMethodSuccess() == true)
        print "Attached message subject: " + origEmail.subject() + "\n";
        # Do whatever else you want..

    end

end