String userName = "test_user_smtp";
m_usersRepository.addUser(userName, "pwd");
smtpProtocol.setSender("");
smtpProtocol.sendCommand("AUTH PLAIN");
smtpProtocol.sendCommand(Base64.encodeAsString("\0" + userName + "\0pwd\0"));
assertEquals("authenticated", 235, smtpProtocol.getReplyCode());
smtpProtocol.addRecipient("mail@sample.com");
assertEquals("expected error", 503, smtpProtocol.getReplyCode());