Recently one of our company's accounts gets a target of spam mails.
This account is already locked, but spam emails never end. Thus, I edit */etc/postfix/header\_check* file as follows:

/^To:.targetuser@ourcompanyshostname.org/ REJECT

I have tested whether I cannot send to a mail to this user and I confirmed that postfix successfully rejects it:)
But, it cannot reject the spammer's mail since the header looks like:

To:< anyname> targetuser@ourcompanyshostname.org

There is an any name in addition to the actual email address that the spammer changes every time. How can I reject this rule?