mail=# CREATE TABLE aliases (
    alias text NOT NULL,
    email text NOT NULL
);
mail=# CREATE TABLE users (
    email text NOT NULL,
    password text NOT NULL,
    maildir text NOT NULL,
    created timestamp with time zone DEFAULT now()
);

mail=# CREATE TABLE domain (
    domain varchar(50) NOT NULL,
    node varchar(50),
    comment varchar(500),
    PRIMARY KEY (domain)
);

virtual_alias_maps = proxy:pgsql:/etc/postfix/virtual_alias_maps.cf
virtual_mailbox_domains = proxy:pgsql:/etc/postfix/virtual_mailbox_domains.cf
virtual_mailbox_maps = proxy:pgsql:/etc/postfix/virtual_mailbox_maps.cf

user = postfix_user
password = your-pass
hosts = localhost
dbname = postfix_db
query = SELECT email FROM aliases WHERE alias='%s'