$ find ~/Maildir/lug-* -type f | \
> xargs grep -il $(echo 'ivfgn' | rot13) | \
> awk -F '/' '{ print $5 }' | \
> sort | uniq -c | sort -rn
     34 lug-hampshire
     31 lug-gl
     19 lug-northwales
     13 lug-sussex
     11 lug-sb
      7 lug-surrey
      3 lug-wolves
      2 lug-sc