#! /usr/bin/env perl
use strict;
use warnings;

open my $f, 'netapsp' or die "open failed: $!";
my $recip = 'some.g.guy@bigcorp.com';
while (<$f>) {
  chomp;
  system "rsh $_ quota report | mail $recip" and die "rsh failed: $!";
}
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Morever, with such a simple program you've little excuse to not use tainting (perldoc perlsec), which would've suggested that you verify what you get from 'netapps' rather than blindly pass it to a shell.