Well, far be it for me to tell a programmer (which I am not) his own business, but I'd think at the very least, one could:
rm -f /var/www/html/squirrelmail/data/*@$CustomerDomain.*
rm -f /var/www/html/squirrelmail/data/$CustomerName.*
Which, BTW, is basically what we've done via the post user removal custom script.
Thanks, as always, for your attention...
-the donco