UTF-8 character issue in sendmail

jk8

We are using the following header code to create an HTML email with utf-8 characters:
my $mailer = new Mail::Mailer('sendmail');

my(%headers) = ('To' => $to_users,
'Cc' => $cc_users,
'From' => $from_user,
'Subject' => $email_subject,
'Date' => $date,
'MIME-Version' => "1.0",
'CONTENT-TYPE' => "text/html; charset=utf-8",
);

This doesn't seem to display the utf-8 characters correctly. It displays some of the German utf-8 characters correctly. But all the Japanese utf-8 characters are not displayed correctly.

Any idea on how to display utf-8 characters in an HTML email using sendmail.

-Thanks
JK