The BCC (blind carbon copy) "header" is not really an e-mail header. Clearly, it cannot be an e-mail header, because if it were, then recipients could examine it, and would no longer be "blind". Rather, BCC is a concept used by mail user agents, and usually implemented to that it appears (to end users) to be a header.

Firstly, you need to understand that the message headers are not used to route the message to its recipients - they are purely informational. Instead, so called envelope addresses (part of SMTP) are used.

And so, to implement BCC, what mail clients do, is simply send the e-mail to the intended recipient using the envelope address, but without adding any message header.

In your particular case, what you need to do is:

1. When constructing the message (Email::MIME->create), do not add a BCC header.
2. When sending the message (sendmail), add an extra option, to (just like your current from option) which takes as its value an arrayref of all the e-mail addresses to which the e-mail should be sent. This includes not just the recipients you want to BCC it to, but also the non-blind recipients (To, CC).

Something along these lines (though it isn't clear from your example what exactly $email_cc and $email_bcc contain - a single address, a comma-separated list, etc).

my $email = Email::MIME->create(
 header_str =>[
         To  => $email_to,
         Cc => $email_cc,
         From => $email_from,
         Subject => $email_subject
 ],
 body_str   =>$email_body,
 attributes => {
         content_type => 'text/html',
         charset => 'utf8',
         encoding => 'quoted-printable'
 }

# ...

try {
 sendmail(
          $email,
          {
           to   => [$email_to, $email_cc, $email_bcc],
           from => $email_from,
           transport => Email::Sender::Transport::SMTP->new({host => $
+SMTP_HOSTNAME,port => $SMTP_PORT})
          }
         );
 }
 catch { print $_->message};
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