virtual_transport = lmtp:unix:private/dovecot-lmtp
virtual_mailbox_domains = mysql:/etc/postfix/mysql-virtual-mailbox-domains.cf
virtual_mailbox_maps = mysql:/etc/postfix/mysql-virtual-mailbox-maps.cf
virtual_alias_maps = mysql:/etc/postfix/mysql-virtual-alias-maps.cf

+----+-----------+------------+----------------------+
| id | domain_id | password   | email                |
+----+-----------+------------+----------------------+
|  1 |         1 | mypassword | [email protected]
|  2 |         1 | mypassword | [email protected]

+----+-----------+------------------------+-----------------------+
| id | domain_id | source                 | destination           |
+----+-----------+------------------------+-----------------------+
|  1 |         1 | @example.com           | [email protected]
|  2 |         1 | [email protected] | [email protected]

user@myserver:~# postmap -q [email protected] mysql:/etc/postfix/mysql-virtual-alias-maps.cf
[email protected]
user@myserver:~# postmap -q [email protected] mysql:/etc/postfix/mysql-virtual-alias-maps.cf
[email protected]