This guide is written under the premise that a mail server has already been configured to send mail from the server
Create a new cronjob
crontab -e
Press i to begin editing and paste the following into the cronjob (change the email address to your email address)
This will check the RAID array every 10 minutes and notify you if there are any changes
*/10 * * * * /sbin/mdadm --monitor --scan --mail=[Your email address] /dev/md0 -1- Updated