Package com.sun.mail.smtp

An SMTP protocol provider for the JavaMail API that provides access to an SMTP server. Refer to RFC 821 for more information.

When sending a message, detailed information on each address that fails is available in an SMTPAddressFailedException chained off the top level SendFailedException that is thrown. In addition, if the mail.smtp.reportsuccess property is set, an SMTPAddressSucceededException will be included in the list for each address that is successful. Note that this will cause a top level SendFailedException to be thrown even though the send was successful.

The SMTP provider also supports ESMTP (RFC 1651). It can optionally use SMTP Authentication (RFC 2554) using the LOGIN, PLAIN, DIGEST-MD5, and NTLM mechanisms (RFC 4616 and RFC 2831).

To use SMTP authentication you'll need to set the mail.smtp.auth property (see below) 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.

    Note that the mail.smtp.user property can be set to provide a default username for the callback, but the password will still need to be supplied explicitly.

    This approach allows you to use the static Transport send method to send messages.

  • Call the Transport connect method explicitly with username and password arguments.

    This approach requires you to explicitly manage a Transport object and use the Transport sendMessage method to send the message. The transport.java demo program demonstrates how to manage a Transport object. The following is roughly equivalent to the static Transport send method, but supplies the needed username and password: 

    Transport tr = session.getTransport("smtp");
tr.connect(smtphost, username, password);
msg.saveChanges();      // don't forget this
tr.sendMessage(msg, msg.getAllRecipients());
tr.close();

When using DIGEST-MD5 authentication, you'll also need to supply an appropriate realm; your mail server administrator can supply this information. You can set this using the mail.smtp.sasl.realm property, or the setSASLRealm method on SMTPTransport.

The SMTP protocol provider can use SASL (RFC 2222) authentication mechanisms on systems that support the javax.security.sasl APIs, such as J2SE 5.0. In addition to the SASL mechanisms that are built into the SASL implementation, users can also provide additional SASL mechanisms of their own design to support custom authentication schemes. See the Java SASL API Programming and Deployment Guide for details. Note that the current implementation doesn't support SASL mechanisms that provide their own integrity or confidentiality layer.

Support for OAuth 2.0 authentication via the XOAUTH2 authentication mechanism is provided either through the SASL support described above or as a built-in authentication mechanism in the SMTP provider. The OAuth 2.0 Access Token should be passed as the password for this mechanism. See OAuth2 Support for details.

SMTP can also optionally request Delivery Status Notifications (RFC 1891). The delivery status will typically be reported using a "multipart/report" (RFC 1892) message type with a "message/delivery-status" (RFC 1894) part. You can use the classes in the com.sun.mail.dsn package to handle these MIME types. Note that you'll need to include dsn.jar in your CLASSPATH as this support is not included in mail.jar.

See below for the properties to enable these features.

Note also that THERE IS NOT SUFFICIENT DOCUMENTATION HERE TO USE THESE FEATURES!!! You will need to read the appropriate RFCs mentioned above to understand what these features do and how to use them. Don't just start setting properties and then complain to us when it doesn't work like you expect it to work. READ THE RFCs FIRST!!!

The SMTP protocol provider supports the CHUNKING extension defined in RFC 3030. Set the mail.smtp.chunksize property to the desired chunk size in bytes. If the server supports the CHUNKING extension, the BDAT command will be used to send the message in chunksize pieces. Note that no pipelining is done so this will be slower than sending the message in one piece. Note also that the BINARYMIME extension described in RFC 3030 is NOT supported.

Properties

The SMTP protocol provider supports the following properties, which may be set in the JavaMail Session object. The properties are always set as strings; the Type column describes how the string is interpreted. For example, use 

        props.put("mail.smtp.port", "888");

to set the mail.smtp.port property, which is of type int.

Note that if you're using the "smtps" protocol to access SMTP over SSL, all the properties would be named "mail.smtps.*".

Name Type Description
mail.smtp.user String Default user name for SMTP.
mail.smtp.host String The SMTP server to connect to.
mail.smtp.port int The SMTP server port to connect to, if the connect() method doesn't explicitly specify one. Defaults to 25.
mail.smtp.connectiontimeout int Socket connection timeout value in milliseconds. This timeout is implemented by java.net.Socket. Default is infinite timeout.
mail.smtp.timeout int Socket read timeout value in milliseconds. This timeout is implemented by java.net.Socket. Default is infinite timeout.
mail.smtp.writetimeout int Socket write timeout value in milliseconds. This timeout is implemented by using a java.util.concurrent.ScheduledExecutorService per connection that schedules a thread to close the socket if the timeout expires. Thus, the overhead of using this timeout is one thread per connection. Default is infinite timeout.
mail.smtp.from String Email address to use for SMTP MAIL command. This sets the envelope return address. Defaults to msg.getFrom() or InternetAddress.getLocalAddress(). NOTE: mail.smtp.user was previously used for this.
mail.smtp.localhost String Local host name used in the SMTP HELO or EHLO command. Defaults to InetAddress.getLocalHost().getHostName(). Should not normally need to be set if your JDK and your name service are configured properly.
mail.smtp.localaddress String Local address (host name) to bind to when creating the SMTP socket. Defaults to the address picked by the Socket class. Should not normally need to be set, but useful with multi-homed hosts where it's important to pick a particular local address to bind to.
mail.smtp.localport int Local port number to bind to when creating the SMTP socket. Defaults to the port number picked by the Socket class.
mail.smtp.ehlo boolean If false, do not attempt to sign on with the EHLO command. Defaults to true. Normally failure of the EHLO command will fallback to the HELO command; this property exists only for servers that don't fail EHLO properly or don't implement EHLO properly.
mail.smtp.auth boolean If true, attempt to authenticate the user using the AUTH command. Defaults to false.
mail.smtp.auth.mechanisms String If set, lists the authentication mechanisms to consider, and the order in which to consider them. Only mechanisms supported by the server and supported by the current implementation will be used. The default is "LOGIN PLAIN DIGEST-MD5 NTLM", which includes all the authentication mechanisms supported by the current implementation except XOAUTH2.
mail.smtp.auth.login.disable boolean If true, prevents use of the AUTH LOGIN command. Default is false.
mail.smtp.auth.plain.disable boolean If true, prevents use of the AUTH PLAIN command. Default is false.
mail.smtp.auth.digest-md5.disable boolean If true, prevents use of the AUTH DIGEST-MD5 command. Default is false.
mail.smtp.auth.ntlm.disable boolean If true, prevents use of the AUTH NTLM command. Default is false.
mail.smtp.auth.ntlm.domain String The NTLM authentication domain.
mail.smtp.auth.ntlm.flags int NTLM protocol-specific flags. See http://curl.haxx.se/rfc/ntlm.html#theNtlmFlags for details.
mail.smtp.auth.xoauth2.disable boolean If true, prevents use of the AUTHENTICATE XOAUTH2 command. Because the OAuth 2.0 protocol requires a special access token instead of a password, this mechanism is disabled by default. Enable it by explicitly setting this property to "false" or by setting the "mail.smtp.auth.mechanisms" property to "XOAUTH2".
mail.smtp.submitter String The submitter to use in the AUTH tag in the MAIL FROM command. Typically used by a mail relay to pass along information about the original submitter of the message. See also the setSubmitter method of SMTPMessage. Mail clients typically do not use this.
mail.smtp.dsn.notify String The NOTIFY option to the RCPT command. Either NEVER, or some combination of SUCCESS, FAILURE, and DELAY (separated by commas).
mail.smtp.dsn.ret String The RET option to the MAIL command. Either FULL or HDRS.
mail.smtp.allow8bitmime boolean If set to true, and the server supports the 8BITMIME extension, text parts of messages that use the "quoted-printable" or "base64" encodings are converted to use "8bit" encoding if they follow the RFC2045 rules for 8bit text.
mail.smtp.sendpartial boolean If set to true, and a message has some valid and some invalid addresses, send the message anyway, reporting the partial failure with a SendFailedException. If set to false (the default), the message is not sent to any of the recipients if there is an invalid recipient address.
mail.smtp.sasl.enable boolean If set to true, attempt to use the javax.security.sasl package to choose an authentication mechanism for login. Defaults to false.
mail.smtp.sasl.mechanisms String A space or comma separated list of SASL mechanism names to try to use.
mail.smtp.sasl.authorizationid String The authorization ID to use in the SASL authentication. If not set, the authentication ID (user name) is used.
mail.smtp.sasl.realm String The realm to use with DIGEST-MD5 authentication.
mail.smtp.sasl.usecanonicalhostname boolean If set to true, the canonical host name returned by InetAddress.getCanonicalHostName is passed to the SASL mechanism, instead of the host name used to connect. Defaults to false.
mail.smtp.quitwait boolean 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.
mail.smtp.reportsuccess boolean If set to true, causes the transport to include an SMTPAddressSucceededException for each address that is successful. Note also that this will cause a SendFailedException to be thrown from the sendMessage method of SMTPTransport even if all addresses were correct and the message was sent successfully.
mail.smtp.socketFactory SocketFactory If set to a class that implements the javax.net.SocketFactory interface, this class will be used to create SMTP sockets. Note that this is an instance of a class, not a name, and must be set using the put method, not the setProperty method.
mail.smtp.socketFactory.class String If set, specifies the name of a class that implements the javax.net.SocketFactory interface. This class will be used to create SMTP sockets.
mail.smtp.socketFactory.fallback boolean If set to true, failure to create a socket using the specified socket factory class will cause the socket to be created using the java.net.Socket class. Defaults to true.
mail.smtp.socketFactory.port int Specifies the port to connect to when using the specified socket factory. If not set, the default port will be used.
mail.smtp.ssl.enable boolean If set to true, use SSL to connect and use the SSL port by default. Defaults to false for the "smtp" protocol and true for the "smtps" protocol.
mail.smtp.ssl.checkserveridentity boolean If set to true, check the server identity as specified by RFC 2595. These additional checks based on the content of the server's certificate are intended to prevent man-in-the-middle attacks. Defaults to false.
mail.smtp.ssl.trust String If set, and a socket factory hasn't been specified, enables use of a MailSSLSocketFactory. If set to "*", all hosts are trusted. If set to a whitespace separated list of hosts, those hosts are trusted. Otherwise, trust depends on the certificate the server presents.
mail.smtp.ssl.socketFactory SSLSocketFactory If set to a class that extends the javax.net.ssl.SSLSocketFactory class, this class will be used to create SMTP SSL sockets. Note that this is an instance of a class, not a name, and must be set using the put method, not the setProperty method.
mail.smtp.ssl.socketFactory.class String If set, specifies the name of a class that extends the javax.net.ssl.SSLSocketFactory class. This class will be used to create SMTP SSL sockets.
mail.smtp.ssl.socketFactory.port int Specifies the port to connect to when using the specified socket factory. If not set, the default port will be used.
mail.smtp.ssl.protocols string Specifies the SSL protocols that will be enabled for SSL connections. The property value is a whitespace separated list of tokens acceptable to the javax.net.ssl.SSLSocket.setEnabledProtocols method.
mail.smtp.ssl.ciphersuites string Specifies the SSL cipher suites that will be enabled for SSL connections. The property value is a whitespace separated list of tokens acceptable to the javax.net.ssl.SSLSocket.setEnabledCipherSuites method.
mail.smtp.starttls.enable boolean If true, enables the use of the STARTTLS command (if supported by the server) to switch the connection to a TLS-protected connection before issuing any login commands. If the server does not support STARTTLS, the connection continues without the use of TLS; see the mail.smtp.starttls.required property to fail if STARTTLS isn't supported. Note that an appropriate trust store must configured so that the client will trust the server's certificate. Defaults to false.
mail.smtp.starttls.required boolean If true, requires the use of the STARTTLS command. If the server doesn't support the STARTTLS command, or the command fails, the connect method will fail. Defaults to false.
mail.smtp.proxy.host string Specifies the host name of an HTTP web proxy server that will be used for connections to the mail server.
mail.smtp.proxy.port string Specifies the port number for the HTTP web proxy server. Defaults to port 80.
mail.smtp.proxy.user string Specifies the user name to use to authenticate with the HTTP web proxy server. By default, no authentication is done.
mail.smtp.proxy.password string Specifies the password to use to authenticate with the HTTP web proxy server. By default, no authentication is done.
mail.smtp.socks.host string Specifies the host name of a SOCKS5 proxy server that will be used for connections to the mail server.
mail.smtp.socks.port string Specifies the port number for the SOCKS5 proxy server. This should only need to be used if the proxy server is not using the standard port number of 1080.
mail.smtp.mailextension String Extension string to append to the MAIL command. The extension string can be used to specify standard SMTP service extensions as well as vendor-specific extensions. Typically the application should use the SMTPTransport method supportsExtension to verify that the server supports the desired service extension. See RFC 1869 and other RFCs that define specific extensions.
mail.smtp.userset boolean If set to true, use the RSET command instead of the NOOP command in the isConnected method. In some cases sendmail will respond slowly after many NOOP commands; use of RSET avoids this sendmail issue. Defaults to false.
mail.smtp.noop.strict boolean If set to true (the default), insist on a 250 response code from the NOOP command to indicate success. The NOOP command is used by the isConnected method to determine if the connection is still alive. Some older servers return the wrong response code on success, some servers don't implement the NOOP command at all and so always return a failure code. Set this property to false to handle servers that are broken in this way. Normally, when a server times out a connection, it will send a 421 response code, which the client will see as the response to the next command it issues. Some servers send the wrong failure response code when timing out a connection. Do not set this property to false when dealing with servers that are broken in this way.

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

In addition to printing debugging output as controlled by the Session configuration, the com.sun.mail.smtp provider logs the same information using Logger as described in the following table:

Logger Name Logging Level Purpose
com.sun.mail.smtp CONFIG Configuration of the SMTPTransport
com.sun.mail.smtp FINE General debugging output
com.sun.mail.smtp.protocol FINEST Complete protocol trace

WARNING: The APIs unique to this package should be considered EXPERIMENTAL. They may be changed in the future in ways that are incompatible with applications using the current APIs.