#!/bin/bash

string="connection_input: conn=11"

tail -n 0 -F /var/log/ldap.log | \
while read LINE
do
echo "$LINE" | grep -q $string
if [ $? = 0 ]
then
echo -e "$string found on $HOSTNAME" | mail -s "LDAP authentication on $(hostname)" teamsupport@yourdomain.com
fi
done