Welcome to LQ.
A script like this should do:
Code:
#!/bin/bash
if [ -f /path/to/file ]; then
echo Your file is there | mail atlight -s "Your file exists"
fi
Make your script executeable:
chmod 700 /path/to/script
Then just add a cron entry to run it every so often eg an hour:
0 * * * * /path/to/script