CREATE TABLE `users` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `login` varchar(45) NOT NULL,
  `email` varchar(255) NOT NULL,
  `md5_Email` char(32) NOT NULL,
  PRIMARY KEY (`id`)
)ENGINE=MyISAM AUTO_INCREMENT=1 DEFAULT CHARSET=latin1;

DELIMITER //
CREATE TRIGGER checkExistEmails BEFORE INSERT ON users
FOR EACH ROW
BEGIN
IF NOT EXISTS (SELECT 1 FROM users WHERE md5_Email = MD5(TRIM(new.email))) THEN
 SET NEW.md5_Email = MD5(TRIM(NEW.email));
ELSE
 SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = 'Email Already Exists';
END IF;
END //
DELIMITER ;

INSERT IGNORE INTO users (`login`,`email`,`md5_Email`)
VALUES ('Login18','ericsanchez@yahoo.com','XXXX'),('Login19','christopher76@hotmail.com','XXXX'),('Login20','ericsanchez@yahoo.com','XXXX'),('Login21','lisa86@hotmail.com','XXXX')

ERROR 1644 (45000): Email Already Exists
MariaDB [DATABASE]> select * from users;
+----+---------+---------------------------+----------------------------------+
| id | login   | email                     | md5_Email                        |
+----+---------+---------------------------+----------------------------------+
|  1 | Login18 | ericsanchez@yahoo.com     | 2eebca4622b871fed0efbd9a8e89802f |
|  2 | Login19 | christopher76@hotmail.com | 3777f449598bcf28f98a9e1711633ced |
+----+---------+---------------------------+----------------------------------+