my $mime_msg = MIME::Lite->new( 
          From => $from_user, 
          To   => $to_users, 
          Bcc  => $bcc_users, 
          Cc  => $cc_users, 
          Subject => $subject, 
          Type => "multipart/related") or die "Error creating MIME body: $!\n";

my $body='/tmp/file.txt'

$mime_msg->attach(Type => 'text/html', Path => $body, Filename => $body ) or die "Error attaching html: $!\n"; 

$smtp->data(); 
$smtp->datasend($message_body); 
$smtp->dataend();
#close connection 
$smtp->quit();