Send email daily from WordPress site

Unfortunately the WordPress cron jobs are only triggered when your site is visited

This is true.

The only way to reliably execute code (even if visitors don’t visit your site) is to use the unix cron functions.

You can just setup a unix cron job that will do a wget on your homepage.

Edit:

You can read this article to figure out how to setup unix cron job.

Just setup the usual wp_cron and schedule it to run at what ever time you want to run it.

After that setup a unix cron job to do a wget on your homepage. This will trigger a page view which in turn will trigger the wp_cron job.