Install

Install msmtp package:

sudo apt install msmtp

Configuration, see ubuntu-rf.org

Use

To add it to the cron tab:

crontab -e

The add new line (to run the check once per hour)

1 * * * * /home/alban/outils/warn-if-broken/warn-if-broken-url.sh >/dev/null 2>&1

Note:

Normaly cron send task outputs (echo) via mail. As the MTA (Mail Transfert Agent), may not be set up, the crontab line redirect the outputs into /dev/null.
No sudo is needed, msmtp and crontab are call with current user.
The logs can be seen using (with sudo): sudo grep CRON /var/log/syslog