Send Mail using spring boot, based on http://www.baeldung.com/spring-email

build.gradle

dependencies {
  compile 'org.springframework.boot:spring-boot-starter-mail:1.5.7.RELEASE'
}

src_main_java_configuration_MailConfiguration.java

@Configuration
public class MailConfiguration {
  @Bean
  public JavaMailSender getJavaMailSender(MailProperties mailProperties) {
      JavaMailSender mailSender = new JavaMailSenderImpl();
      mailSender.setHost(mailProperties.getHost());
      mailSender.setPort(mailProperties.getPort());

      mailSender.setUsername(mailProperties.getUsername());
      mailSender.setPassword(mailProperties.getPassword());

      Properties props = mailSender.getJavaMailProperties();
      props.put("mail.transport.protocol", "smtp");
      props.put("mail.smtp.auth", "true");
      props.put("mail.smtp.starttls.enable", "true");
      props.put("mail.debug", "true");

      return mailSender;
  }
  
  @Bean
  public SimpleMailMessage templateSimpleMessage() {
    SimpleMailMessage message = new SimpleMailMessage();
    message.setText("This is the test email template for your email:\n%s\n");
    return message;
  }
}

src_main_java_services_EmailService.java

public interface EmailService {
    void sendSimpleMessage(String to, String subject, String text);
  
    void sendMessageWithAttachment(String to, String subject, String text, String pathToAttachment);
}

src_main_java_services_EmailServiceImpl.java

@Component
public class EmailServiceImpl implements EmailService {
  
    @Autowired
    public JavaMailSender emailSender;
 
    @Override
    public void sendSimpleMessage(String to, String subject, String text) {
        ...
        SimpleMailMessage message = new SimpleMailMessage(); 
        message.setTo(to); 
        message.setSubject(subject); 
        message.setText(text);
        emailSender.send(message);
        ...
    }
  
  @Override
  public void sendMessageWithAttachment(
  String to, String subject, String text, String pathToAttachment) {
    // ...
     
    MimeMessage message = emailSender.createMimeMessage();
      
    MimeMessageHelper helper = new MimeMessageHelper(message, true);
     
    helper.setTo(to);
    helper.setSubject(subject);
    helper.setText(text);
         
    FileSystemResource file 
      = new FileSystemResource(new File(pathToAttachment));
    helper.addAttachment("Invoice", file);
 
    emailSender.send(message);
    // ...
}  
}

src_main_resources_application.properties

spring.mail.host=smtp.gmail.com
spring.mail.port=587
spring.mail.username=<login user to smtp server>
spring.mail.password=<login password to smtp server>
spring.mail.properties.mail.smtp.auth=true
spring.mail.properties.mail.smtp.starttls.enable=true