Update 17 Oct: I got issue with my hosting and I immediately got email that site is down and in one minute later I got notification that it is up again. So email notification is actually working.

If you have web site in internet sooner or later, you would like to setup monitoring to ensure that site is working and responsive.

Also, if you have site that has low number of visitors then on many hosting platforms your site will be unloaded after some inactive time. And usually startup time is quite long. Depending on hosting, software you are using and how big is your site startup speeds can be quite long. It can be 1-2 seconds long to up