JavaMail API SMTP Servers - JavaMail API

What is JavaMail API SMTP Servers?

SMTP is an acronym for Simple Mail transfer Protocol. it is an internet general for (E-Mail )transmission throughout internet Protocol (IP) networks. SMTP uses TCP port 25. SMTP connections secured by SSL are recognized through 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 get entry to an SMTP server. Following table lists the classes protected on this package:

Class

Description

SMTPMessage

This class is a specialization of the MimeMessage class that allows you to specify various SMTP options and parameters that will be used when this message is sent over SMTP.

SMTPSSLTransport

This class implements the Transport abstract class using SMTP over SSL for message submission and transport.

SMTPTransport

This class implements the Transport abstract class using SMTP for message submission and transport.

The following table lists the exceptions thrown:

Exception

Description

SMTPAddressFailedException

This exception is thrown when the message cannot be sent.

SMTPAddressSucceededException

This exception is chained off a SendFailedException when themail.smtp.reportsuccessproperty is true.

SMTPSenderFailedException

This exception is thrown when the message cannot be sent.

SMTPSendFailedException

This exception is thrown when the message cannot be sent.The exception includes the sender's address, which the mail server rejected.

The com.sun.mail.smtp issuer use SMTP Authentication optionally. to use SMTP authentication you will want to set the mail.smtp.auth assets or provide the SMTP transport with a username and password while connecting to the SMTP server. you may do this the use of one of the following methods:

  • Provide an Authenticator item when creating your mail session and provide the username and password data in the course of the Authenticator callback. mail.smtp.user belongings can be set to offer a default username for the callback, but the password will still need to be provided explicitly. This method lets in you to use the static transport send technique to send messages. for example:


  • Call the transport connect technique explicitly with username and password arguments. for example:


The SMTP protocol company helps the following properties, which can be set inside the JavaMail session item. The properties are always set as strings. as an example:



Here the Type column describes how the string is interpreted.

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. Default is infinite timeout.

mail.smtp.timeout

int

Socket I/O timeout value in milliseconds. 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().

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.

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.

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. 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.

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.

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.

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.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.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.

mail.smtp.socketFactory

Socket Factory

If set to a class that implements the javax.net.SocketFactory interface, this class will be used to create SMTP sockets.

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, checks the server identity as specified by RFC 2595. 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

SSL Socket Factory

If set to a class that extends the javax.net.ssl.SSLSocketFactory class, this class will be used to create SMTP SSL sockets.

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.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. 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.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.

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.

In general, programs need to not want to use the classes on this package at once. instead, they have to use the APIs defined by javax.mail package (and subpackages). Say for example programs need to never construct instances of SMTPTransport directly. instead, they should use the session technique getTransport to collect the right transport object.

Examples to apply SMPT server is demonstrated in chapter Sending Emails

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