How to send multiple emails in one session?
I want to send thousands of开发者_C百科 different emails to different recipients and would like to open the connection to my SMTP and hold it. I hope this is faster then reopen the connection for ervy mail. I would like to use Apache Commons Email for that, but could fall back to the Java Mail API if necessary.
Right now I'am doing this, what opens a closes the connection every time:
HtmlEmail email = new HtmlEmail();
email.setHostName(server.getHostName());
email.setSmtpPort(server.getPort());
email.setAuthenticator(new DefaultAuthenticator(server.getUsername(), server.getPassword()));
email.setTLS(true);
email.setFrom("test@example.com");
email.addTo(to);
email.setSubject(subject);
email.setHtmlMsg(htmlMsg);
email.send();
Here is my performance test class. Sending the mails using one connection is 4 times faster then reopen the connection every time (what happens when you use commons mail). The performance can be pushed further by using multiple threads.
Properties properties = System.getProperties();
properties.put("mail.smtp.host", server);
properties.put("mail.smtp.port", "" + port);
Session session = Session.getInstance(properties);
Transport transport = session.getTransport("smtp");
transport.connect(server, username, password);
for (int i = 0; i < count; i++) {
Message message = new MimeMessage(session);
message.setFrom(new InternetAddress(from));
InternetAddress[] address = {new InternetAddress(to)};
message.setRecipients(Message.RecipientType.TO, address);
message.setSubject(subject + "JavaMail API");
message.setSentDate(new Date());
setHTMLContent(message);
message.saveChanges();
transport.sendMessage(message, address);
}
transport.close();
You can use your earlier code but add the following to get the underlying Session
email.getMailSession();
You can add extra java mail properties by
email.getMailSession().getProperties().put(<key>, <value>);
Have a look at http://java.sun.com/products/javamail/javadocs/com/sun/mail/smtp/package-summary.html. There is an example showing how to send an email. You should be able to send more before calling close() on the Transport.
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