docs: public static boolean verify(String host, String username, String password, int port) throws SMTPException {
  	try {
  	    return _verify(host, username, password, port);
  	}
  	catch (MessagingException e) {
  
  	    // check user
  	    if (!StringUtil.isEmpty(username)) {
  		try {
  		    _verify(host, null, null, port);
  		    throw new SMTPExceptionImpl("can't connect to mail server, authentication settings are invalid");
  		}
  		catch (MessagingException e1) {
  
  		}
  	    }
  	    // check port
  	    if (port > 0 && port != 25) {
  		try {
  		    _verify(host, null, null, 25);
  		    throw new SMTPExceptionImpl("can't connect to mail server, port definition is invalid");
  		}
  		catch (MessagingException e1) {}
  	    }
  
  	    throw new SMTPExceptionImpl("can't connect to mail server");
  	}
      }