# This is untested.
@users = map {
  /^(\S+)[@]/ ? $1 : undef
} grep {
  /(yourdomain|yourotherdomain|yourthirddomain)$/
}  map {
  s/\".*?\"//g;
  (/[<](\S+?)[>]/) ? $1 : undef
} map {
  split /,\s*/, $_
} $headers =~ m/^(?:To|Cc)[:]\s*(.*?)$/mig;
if (not @users) {
  warn "No users.\n";
  @users = ('postmaster');
}