This method is intended primarily for home users who want to be notified via email when apt updates are available to be installed, but who don’t want to have to deal with setting up a full-fledged mail server ….. Maybe you have a server or two, or a few, on your home network that run Debian or Ubuntu or one of their derivatives, that use the apt package manager to do package updates. And maybe you’d like to get an email when new apt updates are available to be installed. Well, here is a relatively easy way to do it.

Source: The easy way to send a notification email when apt updates are available on a Debian or Ubuntu based system, if you don’t have an email server installed – Two “Sort Of” Tech Guys