Correo multiparte / alternativa vs multiparte / mixto

Al crear mensajes de correo electrónico que se supone que para establecer el tipo de contenido a multipart/alternativela hora de enviar HTML y texto o multipart/mixedcuando el envío de texto y archivos adjuntos.

Entonces, ¿qué hacer si desea enviar HTML, texto y archivos adjuntos? Usa ambos?

Hoy llegué a este desafío y encontré estas respuestas útiles, pero no lo suficientemente explícitas para mí.

Editar : Acabo de encontrar el correo electrónico de Apache Commons que lo envuelve muy bien, lo que significa que no necesita saber a continuación.

Si su requisito es un correo electrónico con:

1. versiones de texto y html
2. La versión HTML tiene imágenes incrustadas (en línea)
3. archivos adjuntos

La única estructura que encontré que funciona con Gmail / Outlook / iPad es:

• mezclado
  • alternativa
    • texto
    • relacionado
      • html
      • imagen en línea
      • imagen en línea
  • adjunto archivo
  • adjunto archivo

Y el código es:

import javax.activation.DataHandler;
import javax.activation.DataSource;
import javax.activation.URLDataSource;
import javax.mail.BodyPart;
import javax.mail.MessagingException;
import javax.mail.Multipart;
import javax.mail.internet.MimeBodyPart;
import javax.mail.internet.MimeMultipart;
import java.net.URL;
import java.util.HashMap;
import java.util.List;
import java.util.UUID;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * Created by StrongMan on 25/05/14.
 */
public class MailContentBuilder {

    private static final Pattern COMPILED_PATTERN_SRC_URL_SINGLE = Pattern.compile("src='([^']*)'",  Pattern.CASE_INSENSITIVE);
    private static final Pattern COMPILED_PATTERN_SRC_URL_DOUBLE = Pattern.compile("src=\"([^\"]*)\"",  Pattern.CASE_INSENSITIVE);

    /**
     * Build an email message.
     *
     * The HTML may reference the embedded image (messageHtmlInline) using the filename. Any path portion is ignored to make my life easier
     * e.g. If you pass in the image C:\Temp\dog.jpg you can use <img src="dog.jpg"/> or <img src="C:\Temp\dog.jpg"/> and both will work
     *
     * @param messageText
     * @param messageHtml
     * @param messageHtmlInline
     * @param attachments
     * @return
     * @throws MessagingException
     */
    public Multipart build(String messageText, String messageHtml, List<URL> messageHtmlInline, List<URL> attachments) throws MessagingException {
        final Multipart mpMixed = new MimeMultipart("mixed");
        {
            // alternative
            final Multipart mpMixedAlternative = newChild(mpMixed, "alternative");
            {
                // Note: MUST RENDER HTML LAST otherwise iPad mail client only renders the last image and no email
                addTextVersion(mpMixedAlternative,messageText);
                addHtmlVersion(mpMixedAlternative,messageHtml, messageHtmlInline);
            }
            // attachments
            addAttachments(mpMixed,attachments);
        }

        //msg.setText(message, "utf-8");
        //msg.setContent(message,"text/html; charset=utf-8");
        return mpMixed;
    }

    private Multipart newChild(Multipart parent, String alternative) throws MessagingException {
        MimeMultipart child =  new MimeMultipart(alternative);
        final MimeBodyPart mbp = new MimeBodyPart();
        parent.addBodyPart(mbp);
        mbp.setContent(child);
        return child;
    }

    private void addTextVersion(Multipart mpRelatedAlternative, String messageText) throws MessagingException {
        final MimeBodyPart textPart = new MimeBodyPart();
        textPart.setContent(messageText, "text/plain");
        mpRelatedAlternative.addBodyPart(textPart);
    }

    private void addHtmlVersion(Multipart parent, String messageHtml, List<URL> embeded) throws MessagingException {
        // HTML version
        final Multipart mpRelated = newChild(parent,"related");

        // Html
        final MimeBodyPart htmlPart = new MimeBodyPart();
        HashMap<String,String> cids = new HashMap<String, String>();
        htmlPart.setContent(replaceUrlWithCids(messageHtml,cids), "text/html");
        mpRelated.addBodyPart(htmlPart);

        // Inline images
        addImagesInline(mpRelated, embeded, cids);
    }

    private void addImagesInline(Multipart parent, List<URL> embeded, HashMap<String,String> cids) throws MessagingException {
        if (embeded != null)
        {
            for (URL img : embeded)
            {
                final MimeBodyPart htmlPartImg = new MimeBodyPart();
                DataSource htmlPartImgDs = new URLDataSource(img);
                htmlPartImg.setDataHandler(new DataHandler(htmlPartImgDs));
                String fileName = img.getFile();
                fileName = getFileName(fileName);
                String newFileName = cids.get(fileName);
                boolean imageNotReferencedInHtml = newFileName == null;
                if (imageNotReferencedInHtml) continue;
                // Gmail requires the cid have <> around it
                htmlPartImg.setHeader("Content-ID", "<"+newFileName+">");
                htmlPartImg.setDisposition(BodyPart.INLINE);
                parent.addBodyPart(htmlPartImg);
            }
        }
    }

    private void addAttachments(Multipart parent, List<URL> attachments) throws MessagingException {
        if (attachments != null)
        {
            for (URL attachment : attachments)
            {
                final MimeBodyPart mbpAttachment = new MimeBodyPart();
                DataSource htmlPartImgDs = new URLDataSource(attachment);
                mbpAttachment.setDataHandler(new DataHandler(htmlPartImgDs));
                String fileName = attachment.getFile();
                fileName = getFileName(fileName);
                mbpAttachment.setDisposition(BodyPart.ATTACHMENT);
                mbpAttachment.setFileName(fileName);
                parent.addBodyPart(mbpAttachment);
            }
        }
    }

    public String replaceUrlWithCids(String html, HashMap<String,String> cids)
    {
        html = replaceUrlWithCids(html, COMPILED_PATTERN_SRC_URL_SINGLE, "src='cid:@cid'", cids);
        html = replaceUrlWithCids(html, COMPILED_PATTERN_SRC_URL_DOUBLE, "src=\"cid:@cid\"", cids);
        return html;
    }

    private String replaceUrlWithCids(String html, Pattern pattern, String replacement, HashMap<String,String> cids) {
        Matcher matcherCssUrl = pattern.matcher(html);
        StringBuffer sb = new StringBuffer();
        while (matcherCssUrl.find())
        {
            String fileName = matcherCssUrl.group(1);
            // Disregarding file path, so don't clash your filenames!
            fileName = getFileName(fileName);
            // A cid must start with @ and be globally unique
            String cid = "@" + UUID.randomUUID().toString() + "_" + fileName;
            if (cids.containsKey(fileName))
                cid = cids.get(fileName);
            else
                cids.put(fileName,cid);
            matcherCssUrl.appendReplacement(sb,replacement.replace("@cid",cid));
        }
        matcherCssUrl.appendTail(sb);
        html = sb.toString();
        return html;
    }

    private String getFileName(String fileName) {
        if (fileName.contains("/"))
            fileName = fileName.substring(fileName.lastIndexOf("/")+1);
        return fileName;
    }
}

Y un ejemplo de cómo usarlo desde Gmail

/**
 * Created by StrongMan on 25/05/14.
 */
import com.sun.mail.smtp.SMTPTransport;

import java.net.URL;
import java.security.Security;
import java.util.*;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import javax.activation.DataHandler;
import javax.activation.DataSource;
import javax.activation.URLDataSource;
import javax.mail.*;
import javax.mail.internet.*;

/**
 *
 * http://stackoverflow.com/questions/14744197/best-practices-sending-javamail-mime-multipart-emails-and-gmail
 * http://stackoverflow.com/questions/3902455/smtp-multipart-alternative-vs-multipart-mixed
 *
 *
 *
 * @author doraemon
 */
public class GoogleMail {


    private GoogleMail() {
    }

    /**
     * Send email using GMail SMTP server.
     *
     * @param username GMail username
     * @param password GMail password
     * @param recipientEmail TO recipient
     * @param title title of the message
     * @param messageText message to be sent
     * @throws AddressException if the email address parse failed
     * @throws MessagingException if the connection is dead or not in the connected state or if the message is not a MimeMessage
     */
    public static void Send(final String username, final String password, String recipientEmail, String title, String messageText, String messageHtml, List<URL> messageHtmlInline, List<URL> attachments) throws AddressException, MessagingException {
        GoogleMail.Send(username, password, recipientEmail, "", title, messageText, messageHtml, messageHtmlInline,attachments);
    }

    /**
     * Send email using GMail SMTP server.
     *
     * @param username GMail username
     * @param password GMail password
     * @param recipientEmail TO recipient
     * @param ccEmail CC recipient. Can be empty if there is no CC recipient
     * @param title title of the message
     * @param messageText message to be sent
     * @throws AddressException if the email address parse failed
     * @throws MessagingException if the connection is dead or not in the connected state or if the message is not a MimeMessage
     */
    public static void Send(final String username, final String password, String recipientEmail, String ccEmail, String title, String messageText, String messageHtml, List<URL> messageHtmlInline, List<URL> attachments) throws AddressException, MessagingException {
        Security.addProvider(new com.sun.net.ssl.internal.ssl.Provider());
        final String SSL_FACTORY = "javax.net.ssl.SSLSocketFactory";

        // Get a Properties object
        Properties props = System.getProperties();
        props.setProperty("mail.smtps.host", "smtp.gmail.com");
        props.setProperty("mail.smtp.socketFactory.class", SSL_FACTORY);
        props.setProperty("mail.smtp.socketFactory.fallback", "false");
        props.setProperty("mail.smtp.port", "465");
        props.setProperty("mail.smtp.socketFactory.port", "465");
        props.setProperty("mail.smtps.auth", "true");

        /*
        If set to false, the QUIT command is sent and the connection is immediately closed. If set
        to true (the default), causes the transport to wait for the response to the QUIT command.

        ref :   http://java.sun.com/products/javamail/javadocs/com/sun/mail/smtp/package-summary.html
                http://forum.java.sun.com/thread.jspa?threadID=5205249
                smtpsend.java - demo program from javamail
        */
        props.put("mail.smtps.quitwait", "false");

        Session session = Session.getInstance(props, null);

        // -- Create a new message --
        final MimeMessage msg = new MimeMessage(session);

        // -- Set the FROM and TO fields --
        msg.setFrom(new InternetAddress(username + "@gmail.com"));
        msg.setRecipients(Message.RecipientType.TO, InternetAddress.parse(recipientEmail, false));

        if (ccEmail.length() > 0) {
            msg.setRecipients(Message.RecipientType.CC, InternetAddress.parse(ccEmail, false));
        }

        msg.setSubject(title);

        // mixed
        MailContentBuilder mailContentBuilder = new MailContentBuilder();
        final Multipart mpMixed = mailContentBuilder.build(messageText, messageHtml, messageHtmlInline, attachments);
        msg.setContent(mpMixed);
        msg.setSentDate(new Date());

        SMTPTransport t = (SMTPTransport)session.getTransport("smtps");

        t.connect("smtp.gmail.com", username, password);
        t.sendMessage(msg, msg.getAllRecipients());
        t.close();
    }

}

Use multipart/mixedcon la primera parte como multipart/alternativey partes posteriores para los archivos adjuntos. A su vez, use text/plainy text/htmlpartes dentro de la multipart/alternativeparte.

Un cliente de correo electrónico capaz debería reconocer la multipart/alternativeparte y mostrar la parte de texto o la parte html según sea necesario. También debe mostrar todas las partes posteriores como partes adjuntas.

Lo importante a tener en cuenta aquí es que, en mensajes MIME multiparte, es perfectamente válido tener partes dentro de partes. En teoría, ese anidamiento puede extenderse a cualquier profundidad. Cualquier cliente de correo electrónico razonablemente capaz debería poder procesar recursivamente todas las partes del mensaje.

Los mensajes tienen contenido. El contenido puede ser texto, html, DataHandler o Multipart, y solo puede haber un contenido. Las imágenes prediseñadas solo tienen BodyParts, pero pueden tener más de una. BodyParts, como Mensajes, puede tener contenido que ya se ha descrito.

Un mensaje con HTML, texto y un archivo adjunto se puede ver jerárquicamente de esta manera:

message
  mainMultipart (content for message, subType="mixed")
    ->htmlAndTextBodyPart (bodyPart1 for mainMultipart)
      ->htmlAndTextMultipart (content for htmlAndTextBodyPart, subType="alternative")
        ->textBodyPart (bodyPart2 for the htmlAndTextMultipart)
          ->text (content for textBodyPart)
        ->htmlBodyPart (bodyPart1 for htmlAndTextMultipart)
          ->html (content for htmlBodyPart)
    ->fileBodyPart1 (bodyPart2 for the mainMultipart)
      ->FileDataHandler (content for fileBodyPart1 )

Y el código para construir tal mensaje:

    // the parent or main part if you will
    Multipart mainMultipart = new MimeMultipart("mixed");

    // this will hold text and html and tells the client there are 2 versions of the message (html and text). presumably text
    // being the alternative to html
    Multipart htmlAndTextMultipart = new MimeMultipart("alternative");

    // set text
    MimeBodyPart textBodyPart = new MimeBodyPart();
    textBodyPart.setText(text);
    htmlAndTextMultipart.addBodyPart(textBodyPart);

    // set html (set this last per rfc1341 which states last = best)
    MimeBodyPart htmlBodyPart = new MimeBodyPart();
    htmlBodyPart.setContent(html, "text/html; charset=utf-8");
    htmlAndTextMultipart.addBodyPart(htmlBodyPart);

    // stuff the multipart into a bodypart and add the bodyPart to the mainMultipart
    MimeBodyPart htmlAndTextBodyPart = new MimeBodyPart();
    htmlAndTextBodyPart.setContent(htmlAndTextMultipart);
    mainMultipart.addBodyPart(htmlAndTextBodyPart);

    // attach file body parts directly to the mainMultipart
    MimeBodyPart filePart = new MimeBodyPart();
    FileDataSource fds = new FileDataSource("/path/to/some/file.txt");
    filePart.setDataHandler(new DataHandler(fds));
    filePart.setFileName(fds.getName());
    mainMultipart.addBodyPart(filePart);

    // set message content
    message.setContent(mainMultipart);

Llegué a este problema. Esta arquitectura (de la respuesta de Lain) funcionó para mí. Aquí está la solución en Python.

• mezclado
  • alternativa
    • texto
    • relacionado
      • html
      • imagen en línea
      • imagen en línea
  • adjunto archivo
  • adjunto archivo

Aquí está la función principal de creación de correo electrónico:

def create_message_with_attachment(
    sender, to, subject, msgHtml, msgPlain, attachmentFile):
    """Create a message for an email.

    Args:
      sender: Email address of the sender.
      to: Email address of the receiver.
      subject: The subject of the email message.
      message_text: The text of the email message.
      file: The path to the file to be attached.

    Returns:
      An object containing a base64url encoded email object.
    """
    message = MIMEMultipart('mixed')
    message['to'] = to
    message['from'] = sender
    message['subject'] = subject

    message_alternative = MIMEMultipart('alternative')
    message_related = MIMEMultipart('related')

    message_related.attach(MIMEText(msgHtml, 'html'))
    message_alternative.attach(MIMEText(msgPlain, 'plain'))
    message_alternative.attach(message_related)

    message.attach(message_alternative)

    print "create_message_with_attachment: file:", attachmentFile
    content_type, encoding = mimetypes.guess_type(attachmentFile)

    if content_type is None or encoding is not None:
        content_type = 'application/octet-stream'
    main_type, sub_type = content_type.split('/', 1)
    if main_type == 'text':
        fp = open(attachmentFile, 'rb')
        msg = MIMEText(fp.read(), _subtype=sub_type)
        fp.close()
    elif main_type == 'image':
        fp = open(attachmentFile, 'rb')
        msg = MIMEImage(fp.read(), _subtype=sub_type)
        fp.close()
    elif main_type == 'audio':
        fp = open(attachmentFile, 'rb')
        msg = MIMEAudio(fp.read(), _subtype=sub_type)
        fp.close()
    else:
        fp = open(attachmentFile, 'rb')
        msg = MIMEBase(main_type, sub_type)
        msg.set_payload(fp.read())
        fp.close()
    filename = os.path.basename(attachmentFile)
    msg.add_header('Content-Disposition', 'attachment', filename=filename)
    message.attach(msg)

    return {'raw': base64.urlsafe_b64encode(message.as_string())}

Aquí está el código completo para enviar un correo electrónico que contenga html / text / adjunto:

import httplib2
import os
import oauth2client
from oauth2client import client, tools
import base64
from email.mime.multipart import MIMEMultipart
from email.mime.text import MIMEText
from apiclient import errors, discovery
import mimetypes
from email.mime.image import MIMEImage
from email.mime.audio import MIMEAudio
from email.mime.base import MIMEBase

SCOPES = 'https://www.googleapis.com/auth/gmail.send'
CLIENT_SECRET_FILE1 = 'client_secret.json'
location = os.path.realpath(
    os.path.join(os.getcwd(), os.path.dirname(__file__)))
CLIENT_SECRET_FILE = os.path.join(location, CLIENT_SECRET_FILE1)
APPLICATION_NAME = 'Gmail API Python Send Email'

def get_credentials():
    home_dir = os.path.expanduser('~')
    credential_dir = os.path.join(home_dir, '.credentials')
    if not os.path.exists(credential_dir):
        os.makedirs(credential_dir)
    credential_path = os.path.join(credential_dir,
                                   'gmail-python-email-send.json')
    store = oauth2client.file.Storage(credential_path)
    credentials = store.get()
    if not credentials or credentials.invalid:
        flow = client.flow_from_clientsecrets(CLIENT_SECRET_FILE, SCOPES)
        flow.user_agent = APPLICATION_NAME
        credentials = tools.run_flow(flow, store)
        print 'Storing credentials to ' + credential_path
    return credentials

def SendMessageWithAttachment(sender, to, subject, msgHtml, msgPlain, attachmentFile):
    credentials = get_credentials()
    http = credentials.authorize(httplib2.Http())
    service = discovery.build('gmail', 'v1', http=http)
    message1 = create_message_with_attachment(sender, to, subject, msgHtml, msgPlain, attachmentFile)
    SendMessageInternal(service, "me", message1)

def SendMessageInternal(service, user_id, message):
    try:
        message = (service.users().messages().send(userId=user_id, body=message).execute())
        print 'Message Id: %s' % message['id']
        return message
    except errors.HttpError, error:
        print 'An error occurred: %s' % error
        return "error"

def create_message_with_attachment(
    sender, to, subject, msgHtml, msgPlain, attachmentFile):
    """Create a message for an email.

    Args:
      sender: Email address of the sender.
      to: Email address of the receiver.
      subject: The subject of the email message.
      message_text: The text of the email message.
      file: The path to the file to be attached.

    Returns:
      An object containing a base64url encoded email object.
    """
    message = MIMEMultipart('mixed')
    message['to'] = to
    message['from'] = sender
    message['subject'] = subject

    message_alternative = MIMEMultipart('alternative')
    message_related = MIMEMultipart('related')

    message_related.attach(MIMEText(msgHtml, 'html'))
    message_alternative.attach(MIMEText(msgPlain, 'plain'))
    message_alternative.attach(message_related)

    message.attach(message_alternative)

    print "create_message_with_attachment: file:", attachmentFile
    content_type, encoding = mimetypes.guess_type(attachmentFile)

    if content_type is None or encoding is not None:
        content_type = 'application/octet-stream'
    main_type, sub_type = content_type.split('/', 1)
    if main_type == 'text':
        fp = open(attachmentFile, 'rb')
        msg = MIMEText(fp.read(), _subtype=sub_type)
        fp.close()
    elif main_type == 'image':
        fp = open(attachmentFile, 'rb')
        msg = MIMEImage(fp.read(), _subtype=sub_type)
        fp.close()
    elif main_type == 'audio':
        fp = open(attachmentFile, 'rb')
        msg = MIMEAudio(fp.read(), _subtype=sub_type)
        fp.close()
    else:
        fp = open(attachmentFile, 'rb')
        msg = MIMEBase(main_type, sub_type)
        msg.set_payload(fp.read())
        fp.close()
    filename = os.path.basename(attachmentFile)
    msg.add_header('Content-Disposition', 'attachment', filename=filename)
    message.attach(msg)

    return {'raw': base64.urlsafe_b64encode(message.as_string())}


def main():
    to = "[email protected]"
    sender = "[email protected]"
    subject = "subject"
    msgHtml = "Hi<br/>Html Email"
    msgPlain = "Hi\nPlain Email"
    attachment = "/path/to/file.pdf"
    SendMessageWithAttachment(sender, to, subject, msgHtml, msgPlain, attachment)

if __name__ == '__main__':
    main()

Basándome en el ejemplo de Iain, tenía una necesidad similar de componer estos correos electrónicos con texto sin formato, HTML y archivos adjuntos múltiples, pero usando PHP. Dado que estamos utilizando Amazon SES para enviar correos electrónicos con archivos adjuntos, la API actualmente requiere que cree el correo electrónico desde cero utilizando la función sendRawEmail (...).

Después de mucha investigación (y una frustración mayor que la normal), el problema se resolvió y se publicó el código fuente de PHP para que pueda ayudar a otros que experimentan un problema similar. Espero que esto ayude a alguien: la tropa de monos que forcé a trabajar en este problema ahora están agotados.

Código fuente PHP para enviar correos electrónicos con archivos adjuntos utilizando Amazon SES.

<?php

require_once('AWSSDKforPHP/aws.phar');

use Aws\Ses\SesClient;

/**
 * SESUtils is a tool to make it easier to work with Amazon Simple Email Service
 * Features:
 * A client to prepare emails for use with sending attachments or not
 * 
 * There is no warranty - use this code at your own risk.  
 * @author sbossen with assistance from Michael Deal
 * http://righthandedmonkey.com
 *
 * Update: Error checking and new params input array provided by Michael Deal
 * Update2: Corrected for allowing to send multiple attachments and plain text/html body
 *   Ref: Http://stackoverflow.com/questions/3902455/smtp-multipart-alternative-vs-multipart-mixed/
 */
class SESUtils {

    const version = "1.0";
    const AWS_KEY = "YOUR-KEY";
    const AWS_SEC = "YOUR-SECRET";
    const AWS_REGION = "us-east-1";
    const MAX_ATTACHMENT_NAME_LEN = 60;

    /**
     * Usage:
        $params = array(
          "to" => "[email protected]",
          "subject" => "Some subject",
          "message" => "<strong>Some email body</strong>",
          "from" => "sender@verifiedbyaws",
          //OPTIONAL
          "replyTo" => "[email protected]",
          //OPTIONAL
          "files" => array(
            1 => array(
               "name" => "filename1", 
              "filepath" => "/path/to/file1.txt", 
              "mime" => "application/octet-stream"
            ),
            2 => array(
               "name" => "filename2", 
              "filepath" => "/path/to/file2.txt", 
              "mime" => "application/octet-stream"
            ),
          )
        );

      $res = SESUtils::sendMail($params);

     * NOTE: When sending a single file, omit the key (ie. the '1 =>') 
     * or use 0 => array(...) - otherwise the file will come out garbled
     * ie. use:
     *    "files" => array(
     *        0 => array( "name" => "filename", "filepath" => "path/to/file.txt",
     *        "mime" => "application/octet-stream")
     * 
     * For the 'to' parameter, you can send multiple recipiants with an array
     *    "to" => array("[email protected]", "[email protected]")
     * use $res->success to check if it was successful
     * use $res->message_id to check later with Amazon for further processing
     * use $res->result_text to look for error text if the task was not successful
     * 
     * @param array $params - array of parameters for the email
     * @return \ResultHelper
     */
    public static function sendMail($params) {

        $to = self::getParam($params, 'to', true);
        $subject = self::getParam($params, 'subject', true);
        $body = self::getParam($params, 'message', true);
        $from = self::getParam($params, 'from', true);
        $replyTo = self::getParam($params, 'replyTo');
        $files = self::getParam($params, 'files');

        $res = new ResultHelper();

        // get the client ready
        $client = SesClient::factory(array(
                    'key' => self::AWS_KEY,
                    'secret' => self::AWS_SEC,
                    'region' => self::AWS_REGION
        ));

        // build the message
        if (is_array($to)) {
            $to_str = rtrim(implode(',', $to), ',');
        } else {
            $to_str = $to;
        }

        $msg = "To: $to_str\n";
        $msg .= "From: $from\n";

        if ($replyTo) {
            $msg .= "Reply-To: $replyTo\n";
        }

        // in case you have funny characters in the subject
        $subject = mb_encode_mimeheader($subject, 'UTF-8');
        $msg .= "Subject: $subject\n";
        $msg .= "MIME-Version: 1.0\n";
        $msg .= "Content-Type: multipart/mixed;\n";
        $boundary = uniqid("_Part_".time(), true); //random unique string
        $boundary2 = uniqid("_Part2_".time(), true); //random unique string
        $msg .= " boundary=\"$boundary\"\n";
        $msg .= "\n";

        // now the actual body
        $msg .= "--$boundary\n";

        //since we are sending text and html emails with multiple attachments
        //we must use a combination of mixed and alternative boundaries
        //hence the use of boundary and boundary2
        $msg .= "Content-Type: multipart/alternative;\n";
        $msg .= " boundary=\"$boundary2\"\n";
        $msg .= "\n";
        $msg .= "--$boundary2\n";

        // first, the plain text
        $msg .= "Content-Type: text/plain; charset=utf-8\n";
        $msg .= "Content-Transfer-Encoding: 7bit\n";
        $msg .= "\n";
        $msg .= strip_tags($body); //remove any HTML tags
        $msg .= "\n";

        // now, the html text
        $msg .= "--$boundary2\n";
        $msg .= "Content-Type: text/html; charset=utf-8\n";
        $msg .= "Content-Transfer-Encoding: 7bit\n";
        $msg .= "\n";
        $msg .= $body; 
        $msg .= "\n";
        $msg .= "--$boundary2--\n";

        // add attachments
        if (is_array($files)) {
            $count = count($files);
            foreach ($files as $file) {
                $msg .= "\n";
                $msg .= "--$boundary\n";
                $msg .= "Content-Transfer-Encoding: base64\n";
                $clean_filename = self::clean_filename($file["name"], self::MAX_ATTACHMENT_NAME_LEN);
                $msg .= "Content-Type: {$file['mime']}; name=$clean_filename;\n";
                $msg .= "Content-Disposition: attachment; filename=$clean_filename;\n";
                $msg .= "\n";
                $msg .= base64_encode(file_get_contents($file['filepath']));
                $msg .= "\n--$boundary";
            }
            // close email
            $msg .= "--\n";
        }

        // now send the email out
        try {
            $ses_result = $client->sendRawEmail(
                    array(
                'RawMessage' => array(
                    'Data' => base64_encode($msg)
                )
                    ), array(
                'Source' => $from,
                'Destinations' => $to_str
                    )
            );
            if ($ses_result) {
                $res->message_id = $ses_result->get('MessageId');
            } else {
                $res->success = false;
                $res->result_text = "Amazon SES did not return a MessageId";
            }
        } catch (Exception $e) {
            $res->success = false;
            $res->result_text = $e->getMessage().
                    " - To: $to_str, Sender: $from, Subject: $subject";
        }
        return $res;
    }

    private static function getParam($params, $param, $required = false) {
        $value = isset($params[$param]) ? $params[$param] : null;
        if ($required && empty($value)) {
            throw new Exception('"'.$param.'" parameter is required.');
        } else {
            return $value;
        }
    }

    /**
    Clean filename function - to get a file friendly 
    **/
    public static function clean_filename($str, $limit = 0, $replace=array(), $delimiter='-') {
        if( !empty($replace) ) {
            $str = str_replace((array)$replace, ' ', $str);
        }

        $clean = iconv('UTF-8', 'ASCII//TRANSLIT', $str);
        $clean = preg_replace("/[^a-zA-Z0-9\.\/_| -]/", '', $clean);
        $clean = preg_replace("/[\/| -]+/", '-', $clean);

        if ($limit > 0) {
            //don't truncate file extension
            $arr = explode(".", $clean);
            $size = count($arr);
            $base = "";
            $ext = "";
            if ($size > 0) {
                for ($i = 0; $i < $size; $i++) {
                    if ($i < $size - 1) { //if it's not the last item, add to $bn
                        $base .= $arr[$i];
                        //if next one isn't last, add a dot
                        if ($i < $size - 2)
                            $base .= ".";
                    } else {
                        if ($i > 0)
                            $ext = ".";
                        $ext .= $arr[$i];
                    }
                }
            }
            $bn_size = mb_strlen($base);
            $ex_size = mb_strlen($ext);
            $bn_new = mb_substr($base, 0, $limit - $ex_size);
            // doing again in case extension is long
            $clean = mb_substr($bn_new.$ext, 0, $limit); 
        }
        return $clean;
    }

}

class ResultHelper {

    public $success = true;
    public $result_text = "";
    public $message_id = "";

}

?>

Gran respuesta Lain!

Hubo un par de cosas que hice para que esto funcione en un conjunto más amplio de dispositivos. Al final enumeraré los clientes en los que probé.

1. Agregué un nuevo constructor de compilación que no contenía los archivos adjuntos de parámetros y no usaba MimeMultipart ("mixto"). No es necesario mezclar si solo envía imágenes en línea.

   public Multipart build(String messageText, String messageHtml, List<URL> messageHtmlInline) throws MessagingException {
   
       final Multipart mpAlternative = new MimeMultipart("alternative");
       {
           //  Note: MUST RENDER HTML LAST otherwise iPad mail client only renders 
           //  the last image and no email
               addTextVersion(mpAlternative,messageText);
               addHtmlVersion(mpAlternative,messageHtml, messageHtmlInline);
       }
   
       return mpAlternative;
   }
   

2. En el método addTextVersion agregué charset al agregar contenido que probablemente podría / debería pasarse, pero solo lo agregué estáticamente.

   textPart.setContent(messageText, "text/plain");
   to
   textPart.setContent(messageText, "text/plain; charset=UTF-8");
   

3. El último elemento fue agregar al método addImagesInline. Agregué la configuración del nombre de archivo de la imagen al encabezado con el siguiente código. Si no hace esto, al menos en el cliente de correo predeterminado de Android tendrá imágenes en línea que tienen un nombre de Desconocido y no las descargará automáticamente ni las presentará por correo electrónico.

   for (URL img : embeded) {
       final MimeBodyPart htmlPartImg = new MimeBodyPart();
       DataSource htmlPartImgDs = new URLDataSource(img);
       htmlPartImg.setDataHandler(new DataHandler(htmlPartImgDs));
       String fileName = img.getFile();
       fileName = getFileName(fileName);
       String newFileName = cids.get(fileName);
       boolean imageNotReferencedInHtml = newFileName == null;
       if (imageNotReferencedInHtml) continue;
       htmlPartImg.setHeader("Content-ID", "<"+newFileName+">");
       htmlPartImg.setDisposition(BodyPart.INLINE);
       **htmlPartImg.setFileName(newFileName);**
       parent.addBodyPart(htmlPartImg);
   }
   

Finalmente, esta es la lista de clientes que probé. Outlook 2010, aplicación web de Outlook, Internet Explorer 11, Firefox, Chrome, Outlook usando la aplicación nativa de Apple, correo electrónico a través de Gmail: cliente de correo del navegador, Internet Explorer 11, Firefox, Chrome, cliente de correo predeterminado de Android, cliente de correo predeterminado de iPhone osx, Gmail cliente de correo en Android, cliente de correo de Gmail en iPhone, correo electrónico que pasa por Yahoo: cliente de correo del navegador, Internet Explorer 11, Firefox, Chrome, cliente de correo predeterminado de Android, cliente de correo predeterminado de iPhone osx.

Espero que ayude a alguien más.

Aquí está lo mejor: mensaje mime multiparte / mixto con archivos adjuntos e imágenes en línea

E imagen: https://www.qcode.co.uk/images/mime-nesting-structure.png

From: [email protected]
To: to@@qcode.co.uk
Subject: Example Email
MIME-Version: 1.0
Content-Type: multipart/mixed; boundary="MixedBoundaryString"

--MixedBoundaryString
Content-Type: multipart/related; boundary="RelatedBoundaryString"

--RelatedBoundaryString
Content-Type: multipart/alternative; boundary="AlternativeBoundaryString"

--AlternativeBoundaryString
Content-Type: text/plain;charset="utf-8"
Content-Transfer-Encoding: quoted-printable

This is the plain text part of the email.

--AlternativeBoundaryString
Content-Type: text/html;charset="utf-8"
Content-Transfer-Encoding: quoted-printable

<html>
  <body>=0D
    <img src=3D=22cid:masthead.png=40qcode.co.uk=22 width 800 height=3D80=
 =5C>=0D
    <p>This is the html part of the email.</p>=0D
    <img src=3D=22cid:logo.png=40qcode.co.uk=22 width 200 height=3D60 =5C=
>=0D
  </body>=0D
</html>=0D

--AlternativeBoundaryString--

--RelatedBoundaryString
Content-Type: image/jpgeg;name="logo.png"
Content-Transfer-Encoding: base64
Content-Disposition: inline;filename="logo.png"
Content-ID: <[email protected]>

amtsb2hiaXVvbHJueXZzNXQ2XHVmdGd5d2VoYmFmaGpremxidTh2b2hydHVqd255aHVpbnRyZnhu
dWkgb2l1b3NydGhpdXRvZ2hqdWlyb2h5dWd0aXJlaHN1aWhndXNpaHhidnVqZmtkeG5qaG5iZ3Vy
...
...
a25qbW9nNXRwbF0nemVycHpvemlnc3k5aDZqcm9wdHo7amlodDhpOTA4N3U5Nnkwb2tqMm9sd3An
LGZ2cDBbZWRzcm85eWo1Zmtsc2xrZ3g=

--RelatedBoundaryString
Content-Type: image/jpgeg;name="masthead.png"
Content-Transfer-Encoding: base64
Content-Disposition: inline;filename="masthead.png"
Content-ID: <[email protected]>

aXR4ZGh5Yjd1OHk3MzQ4eXFndzhpYW9wO2tibHB6c2tqOTgwNXE0aW9qYWJ6aXBqOTBpcjl2MC1t
dGlmOTA0cW05dGkwbWk0OXQwYVttaXZvcnBhXGtsbGo7emt2c2pkZnI7Z2lwb2F1amdpNTh1NDlh
...
...
eXN6dWdoeXhiNzhuZzdnaHQ3eW9zemlqb2FqZWt0cmZ1eXZnamhka3JmdDg3aXV2dWd5aGVidXdz
dhyuhehe76YTGSFGA=

--RelatedBoundaryString--

--MixedBoundaryString
Content-Type: application/pdf;name="Invoice_1.pdf"
Content-Transfer-Encoding: base64
Content-Disposition: attachment;filename="Invoice_1.pdf"

aGZqZGtsZ3poZHVpeWZoemd2dXNoamRibngganZodWpyYWRuIHVqO0hmSjtyRVVPIEZSO05SVURF
SEx1aWhudWpoZ3h1XGh1c2loZWRma25kamlsXHpodXZpZmhkcnVsaGpnZmtsaGVqZ2xod2plZmdq
...
...
a2psajY1ZWxqanNveHV5ZXJ3NTQzYXRnZnJhZXdhcmV0eXRia2xhanNueXVpNjRvNWllc3l1c2lw
dWg4NTA0

--MixedBoundaryString
Content-Type: application/pdf;name="SpecialOffer.pdf"
Content-Transfer-Encoding: base64
Content-Disposition: attachment;filename="SpecialOffer.pdf"

aXBvY21odWl0dnI1dWk4OXdzNHU5NTgwcDN3YTt1OTQwc3U4NTk1dTg0dTV5OGlncHE1dW4zOTgw
cS0zNHU4NTk0eWI4OTcwdjg5MHE4cHV0O3BvYTt6dWI7dWlvenZ1em9pdW51dDlvdTg5YnE4N3Z3
...
...
OTViOHk5cDV3dTh5bnB3dWZ2OHQ5dTh2cHVpO2p2Ymd1eTg5MGg3ajY4bjZ2ODl1ZGlvcjQ1amts
dfnhgjdfihn=

--MixedBoundaryString--

.

Esquema multiparte / relacionado / alternativo

Header
|From: email
|To: email
|MIME-Version: 1.0
|Content-Type: multipart/mixed; boundary="boundary1";
Message body
|multipart/mixed --boundary1
|--boundary1
|   multipart/related --boundary2
|   |--boundary2
|   |   multipart/alternative --boundary3
|   |   |--boundary3
|   |   |text/plain
|   |   |--boundary3
|   |   |text/html
|   |   |--boundary3--
|   |--boundary2    
|   |Inline image
|   |--boundary2    
|   |Inline image
|   |--boundary2--
|--boundary1    
|Attachment1
|--boundary1
|Attachment2
|--boundary1
|Attachment3
|--boundary1--
|
.

Subtipo mixto

El subtipo "mixto" de "multiparte" está diseñado para usarse cuando las partes del cuerpo son independientes y necesitan agruparse en un orden particular. Cualquier subtipo "multiparte" que una implementación no reconozca debe ser tratado como un subtipo "mixto".

Subtipo Alternativo

El tipo "multiparte / alternativa" es sintácticamente idéntico a "multiparte / mixto", pero la semántica es diferente. En particular, cada una de las partes del cuerpo es una versión "alternativa" de la misma información

Fuente