https://dustymabe.com/2012/01/29/monitor-raid-arrays-and-get-e-mail-alerts-using-mdadm/

I decided at this point that I need a better way to be notified when things like this happen. It turns out you can configure mdadm to monitor the raid arrays and notify you via email when errors occur. To achieve this effect I added the following line to the /etc/mdadm.conf file:

MAILADDR dustymabe@gmail.com

Now, as long as mdadm is configured to run and monitor the arrays (on SUSE it is the mdadmd service), then you will get email alerts when things go wrong.

To verify your emails are working you can use the following command, which will send out a test email:

sudo mdadm --monitor --scan --test -1