Contact Form in Open edX (Zendesk 503 Service Unavailable)


We have installed an open edX instance (Juniper release)
I noticed that the contact form in /support/contact_us makes a request like this:

A POST request is sent to:

That is answered with a “503 Service Unavailable” response.

AT the same time, I notice that in the lms container logs like this:

When looking at the logs with tutor logs there is this in the lms_1 container:

lms_1            | 2020-08-19 13:13:33,036 ERROR 76 [openedx.core.djangoapps.zendesk_proxy.utils] [user 3] - zendesk_proxy action required
lms_1            | zendesk not configured

So, what is the requirement to have the contact form configured. I did not find documentation about this.
Do you know where I could get information to do it?

Is having zendesk a requirement or could this be changed so the requests are sent to another system, or forwarded to a SMTP relay?