ConfigServer Community Forum

This is obvious, no?

Is there any documentation available on how to do this?

You may wish to start with the documentation: https://download.configserver.com/csf/readme.txt.
My understanding is that CSF uses the host linux 'sendmail' command to send email; thus it is your host server email setup where your authentication must take place or bypassing authentication for CSF.

You may wish to explore this setting in the configuration file for CSF (csf.conf).

This option redirects outgoing SMTP connections destined for remote servers
for non-bypass users to the local SMTP server to force local relaying of
email. Such email may require authentication (SMTP AUTH)
SMTP_REDIRECT =

I did nothing special when installing and setting up CSF for my server; it just works, including email alerts and logs.