message.setBody(MAIL_CONTENTS);
message.setMimeType(TEXT_HTML);
Attachment attachment = new Attachment();
attachment.setInputStream(new ByteArrayInputStream(ATTACHMENT.getBytes()));
attachment.setMimeType(TEXT_PLAIN);
message.addAttachment(attachment);
assertEquals("SMTP server should be now empty", 0, mailServer.getMessages().size());
assertFalse(isEmailMessageSent(MAIL_SUBJECT));
service.sendMessage(message);
Thread.sleep(ONE_SECOND);