is possible reject TO: undisclosed-recipients???

[cassiol]

Hello everyone,

i try block undisclosed-recipients with header_check, but no work.
This is my header check

/^To:.*recipient*/ REDIRECT

anyone has another idea?

thanks for any advice

update 1:
when ZWC send bcc, not input header To: undisclosed-recipients:; why?????
header check is correct and work, but not with ZWC.