Hi, in that example, I do a refactoring on Email class of the post Send Mail with Attachment.

Mail.java

package com.christianborges.mail;

import java.io.IOException;
import java.util.Properties;

import javax.activation.DataHandler;
import javax.mail.Authenticator;
import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.Multipart;
import javax.mail.PasswordAuthentication;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeBodyPart;
import javax.mail.internet.MimeMessage;
import javax.mail.internet.MimeMultipart;

import com.christianborges.mail.attachment.InputStreamDataSource;

public class Mail {

	private static final String TRUE = "true";
	private static final String MAIL_TRANSPORT_PROTOCOL = "smtp";
	private static final int THREAD_INTERVAL_SEND_MAIL = 10;

	private InputStreamDataSource attachmentStream;
	private MimeBodyPart attachFilePart;

	public void send(final MailMessage mailMessage) throws Exception {

		if (mailMessage == null)
			throw new NullPointerException();

		final Message mimeMesssage = new MimeMessage( this.createMailSession(mailMessage) );
		final MimeBodyPart mimeBodyPart = new MimeBodyPart();

		mimeMesssage.setFrom(mailMessage.getFromAddress());
		mimeMesssage.setSubject(mailMessage.getSubject());

		mimeBodyPart.setContent(mailMessage.getBody(), mailMessage.getContentType().getBaseType());

		this.setAttachment(mailMessage, mimeMesssage, mimeBodyPart);

		for (InternetAddress toAddress : mailMessage.getToAddressess()) {
			mimeMesssage.setRecipient(Message.RecipientType.TO, toAddress);
			Transport.send(mimeMesssage);
			Thread.sleep(THREAD_INTERVAL_SEND_MAIL);
		}

		this.attachFilePart = null;
		this.attachmentStream = null;
	}

	private Session createMailSession(final MailMessage mailMessage) {

		final Properties sessionProperties = new Properties();

		sessionProperties.setProperty("mail.transport.protocol", MAIL_TRANSPORT_PROTOCOL);
		sessionProperties.put("mail.smtp.host", mailMessage.getMailSecurity().getSmtpServer());
		sessionProperties.put("mail.smtp.auth", TRUE);
		sessionProperties.put("mail.smtp.port", mailMessage.getMailSecurity().getSmtpPort());

		if (mailMessage.getMailSecurity().isSSL()) {
			sessionProperties.put("mail.smtp.starttls.enable", TRUE);
		}

		final Authenticator auth = new Authenticator() {

			@Override
			public PasswordAuthentication getPasswordAuthentication() {
				return new PasswordAuthentication(mailMessage.getMailSecurity().getUser(), mailMessage.getMailSecurity().getPasswd());
			}
		};

		return Session.getInstance(sessionProperties, auth);
	}

	private void setAttachment(final MailMessage mailMessage, final Message mimeMesssage, final MimeBodyPart mimeBodyPart)
			throws IOException, MessagingException {

		if (mailMessage.hasAttachment()) {
			attachmentStream = new InputStreamDataSource(mailMessage.getMailAttachment());
			attachFilePart = new MimeBodyPart();

			attachFilePart.setDataHandler(new DataHandler(attachmentStream));
			attachFilePart.setFileName(attachmentStream.getName());

			final Multipart mimeMultipart = new MimeMultipart();
			mimeMultipart.addBodyPart(mimeBodyPart);

			if (attachFilePart != null) {
				mimeMultipart.addBodyPart(attachFilePart);
			}

			mimeMesssage.setContent(mimeMultipart);
		}
	}
}

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