sub mail {

  foreach my $user (@users) {

    print "recipient is: $user\n";

    my %message = ( To  => $user,
          From          => 'root@flagmail.wr.usgs.gov',
          Subject       => 'Disk usage summary',
          Message       => $summary
          );

    sendmail(%message) or die $Mail::Sendmail::error;
  }

  print "Log says: \n", $Mail::Sendmail::log;

}