Spring Integration currently provides support for outbound email only with the MailTargetAdapter. This adapter delegates to a configured instance of Spring's JavaMailSender, and its various mapping strategies use Spring's MailMessage abstraction. By default text-based mails are created when the handled message has a String-based payload. If the message payload is a byte array, then that will be mapped to an attachment.

The adapter also delegates to a MailHeaderGenerator for providing the mail's properties, such as the recipients (TO, CC, and BCC), the from/reply-to, and the subject.

public interface MailHeaderGenerator {
    void populateMailMessageHeader(MailMessage mailMessage, Message<?> message);
}

The default implementation will look for attributes in the MessageHeader with the following constants defining the keys:

MailAttributeKeys.SUBJECT
MailAttributeKeys.TO
MailAttributeKeys.CC
MailAttributeKeys.BCC
MailAttributeKeys.FROM
MailAttributeKeys.REPLY_TO

A static implementation is also available out-of-the-box and may be useful for testing. However, when customizing, the properties would typically be generated dynamically based on the message itself. The following is an example of a configured mail adapter.

<bean id="mailTargetAdapter"
    class="org.springframework.integration.adapter.mail.MailTargetAdapter">
    <property name="mailSender" ref="javaMailSender"/>
    <property name="headerGenerator" ref="dynamicMailMessageHeaderGenerator"/>
</bean>