JavaMail API - SMTP Servers

SMTP is an acronym for Simple Mail Transfer Protocol. It is an Internet standard for electronic mail (e-mail) transmission across Internet Protocol (IP) networks. SMTP uses TCP port 25. SMTP connections secured by SSL are known by the shorthand SMTPS, though SMTPS is not a protocol in its own right.

JavaMail API has package com.sun.mail.smtp which act as SMTP protocol provider to access an SMTP server. Following table psts the classes included in this package:

The following table psts the exceptions thrown:

The com.sun.mail.smtp provider use SMTP Authentication optionally. To use SMTP authentication you ll need to set the mail.smtp.auth property or provide the SMTP Transport with a username and password when connecting to the SMTP server. You can do this using one of the following approaches:

Provide an Authenticator object when creating your mail Session and provide the username and password information during the Authenticator callback. mail.smtp.user property can be set to provide a default username for the callback, but the password will still need to be suppped exppcitly. This approach allows you to use the static Transport send method to send messages. For example:

Transport.send(message);

Call the Transport connect method exppcitly with username and password arguments. For example:

Transport tr = session.getTransport("smtp");
tr.connect(smtphost, username, password);
msg.saveChanges();
tr.sendMessage(msg, msg.getAllRecipients());
tr.close();

The SMTP protocol provider supports the following properties, which may be set in the JavaMail Session object. The properties are always set as strings. For example:

 props.put("mail.smtp.port", "587");

Here the Type column describes how the string is interpreted.

In general, apppcations should not need to use the classes in this package directly. Instead, they should use the APIs defined by javax.mail package (and subpackages). Say for example apppcations should never construct instances of SMTPTransport directly. Instead, they should use the Session method getTransport to acquire an appropriate Transport object.

Examples to use SMPT server is demonstrated in chapter Sending Emails.