As VSarkiss says, you may need to parse the first (i.e. most recent-- assuming you haven't already used sendmail after receiving the mail from the outside world) "recieved" header 
Received: from mail.fromdomain.com (localhost [127.0.0.1])
          by mail.domain.com (x.x.x/x.x.x) with ESMTP id Mxxxxxx
          for <user_ID@domain.com>; Fri, 29 Jun 2001 01:23:45

[download]
for the <user_ID@domain.com> since that should have the name of the mailbox the email is intended for.

In reply to (ichimunki) Re x 3: Getting BCC: header from a message. by ichimunki
in thread Getting BCC: header from a message. by unixdown

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