support user+extension@domain style addresses using postfix

[AubreyH]

Hi,

I would like to support user+extension@domain addresses [user+extension@domain -> user@domain] (using postfix through plesk).

We have set:
main.cf

recipient_delimiter = +

master.cf (on the maildrop config):

-d ${user}@${domain} ${extension} ${recipient} ${user} ${nexthop}

@see http://www.postfix.org/MAILDROP_README.html
@see http://superuser.com/questions/587458/postfix-unlimited-per-user-addresses-via-sign

Though it still fails and the error log (mail.err) says:

DATE HOST postfix-local[PID]: Unknown user: USER+ETC@DOMAIN

I know that the directory name "USER+ETC" is being looked for.. and yeah it does not exist... so all current settings seem to be ignored. Something is still looking for "USER+ETC" as a delivery directory. I am assuming that the maildrop is not used as plesk has its own "plesk_virtual"...
Is it something that needs to be changed on the master.cf "plesk_virtual" config? If I add the same -d option to the "plesk_virtual" config; all mail fails with "Local delivery is disabled due to server misconfigurations"

Am I missing something? How can I support user+etc@domain addresses using a plesk/postfix combo?

Thanks, Aubrey

p.s. Sorry if question has already been answered (I could not find it).. s-)