SMTPServerRule.java

public class SMTPServerRule extends ExternalResource {

   private GreenMail smtpServer;
   private String hostname;
   private int port;

   public SMTPServerRule() {
       this(25);
   }

   public SMTPServerRule(int port) {
       this("localhost", port);
   }

   public SMTPServerRule(String hostname, int port) {
       this.hostname = hostname;
       this.port = port;
   }


   @Override
   protected void before() throws Throwable {
       super.before();

       smtpServer = new GreenMail(new ServerSetup(port, hostname, "smtp"));
       smtpServer.start();
   }

   public List<ExpectedMail> getMessages() {
       return Lists.newArrayList(smtpServer.getReceivedMessages()).stream()
           .parallel()
           .map(mimeMessage -> ExpectedMail.transformMimeMessage(mimeMessage)).collect(Collectors.toList());
   }

   @Override
   protected void after() {
       super.after();
       smtpServer.stop();
   }
}