I used to send emails that way. You might have better luck using MIME::Lite. If you can't just pipe the mail to /bin/mail, try sending it as text attachment. Text attachments load in the message body. It has worked well for me:

my $message = join("\n" ,@messages);

use MIME::Lite;

my $msg = MIME::Lite->new(
    From    => 'admin@yourdomain.net',
    To      => 'users@yourdomain.net',
    Subject => 'CM Audit Daily Changes Notification',
);

$msg->attach(
    Type    => 'TEXT',
    Data    => $message
);

$msg->send();
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