I've set up that tiny script and saved it as "newmail" in /usr/local/bin and added a line at the end of /etc/bash/bashrc
And here it is:
if [ -d ~/.maildir ]
newmail=`find ~/.maildir/new -type f | wc -l`
if [ $newmail -gt 0 ]
echo "You have $newmail new mails."
echo "No new mail for you."
This script works out-of-the-box for the Gentoo and Funtoo distro, YMMV.