@Test public void failedMailServerConnect() { MockJavaMailSender sender = new MockJavaMailSender(); sender.setHost(null); sender.setUsername("username"); sender.setPassword("password"); SimpleMailMessage simpleMessage1 = new SimpleMailMessage(); try { sender.send(simpleMessage1); fail("Should have thrown MailSendException"); } catch (MailSendException ex) { // expected ex.printStackTrace(); assertTrue(ex.getFailedMessages() != null); assertEquals(1, ex.getFailedMessages().size()); assertSame(simpleMessage1, ex.getFailedMessages().keySet().iterator().next()); assertSame(ex.getCause(), ex.getFailedMessages().values().iterator().next()); } }