mysql> desc email;
+---------------+--------------+------+-----+---------+----------------+
| Field         | Type         | Null | Key | Default | Extra          |
+---------------+--------------+------+-----+---------+----------------+
| message_id    | int(10)      | NO   | PRI | NULL    | auto_increment | 
| quarantine_id | varchar(20)  | NO   | PRI | NULL    |                | 
| type          | varchar(8)   | NO   |     | NULL    |                | 
| sender        | varchar(255) | NO   |     | NULL    |                | 
| subject       | varchar(255) | NO   |     | NULL    |                | 
| date          | date         | NO   |     | NULL    |                | 
+---------------+--------------+------+-----+---------+----------------+
6 rows in set (0.00 sec)

mysql> desc reference;
+------------+---------+------+-----+---------+-------+
| Field      | Type    | Null | Key | Default | Extra |
+------------+---------+------+-----+---------+-------+
| account_id | int(10) | NO   |     | NULL    |       | 
| message_id | int(10) | NO   |     | NULL    |       | 
+------------+---------+------+-----+---------+-------+
2 rows in set (0.00 sec)

mysql> desc user;
+---------------+--------------+------+-----+---------+----------------+
| Field         | Type         | Null | Key | Default | Extra          |
+---------------+--------------+------+-----+---------+----------------+
| account_id    | int(10)      | NO   | PRI | NULL    | auto_increment | 
| primary_email | varchar(255) | NO   | PRI | NULL    |                | 
+---------------+--------------+------+-----+---------+----------------+
2 rows in set (0.00 sec)