[SDNF] Sender Domain Not Found

Hello,

I am trying to use MailChannels in my pages using the function found on Cloudflare documentation:

let mail_request = {
            "method": "POST",
            "headers": {
                "content-type": "application/json",
            },
            "body": JSON.stringify({
                "personalizations": [
                    {
                        "to": [
                            {"email": "<send to email>", "name": "Recepient"}
                        ],
                        "dkim_domain": "<my domain>",
                        "dkim_selector": "mailchannels",
                        "dkim_private_key": context.env.DKIM_PRIVATE_KEY
                    }
                ],
                "from": {
                    "email": "[email protected]<my domain>",
                    "name": "Me",
                },
                "subject": output['firstname'] + " " + output['name'],
                "content": [{
                    "type": "text/plain",
                    "value": _createMessageContent(output),
                }],
            }),
        };

        // only send the mail on "POST", to avoid spiders, etc.
        if( context.request.method == "POST" ) {
            let send_request = new Request("https://api.mailchannels.net/tx/v1/send", mail_request);
            const resp = await fetch(send_request);
            const respText = await resp.text();
            if (resp.status != 200 || resp.status != 202) {
                return new Response('Error sending response: ' + respText, { status: 400 });
            }
        }

But I am getting the following error:

Error sending response: Internal Server Error {"errors":["Failed to send email: 550 5.1.2 [SDNF] Sender Domain Not Found. https://console.mailchannels.net/insights/bounce?auid=cloudflare\u0026sender=rsvp%40<my domain>\u0026txid=1719219f365d9c74"]}

What am I missing ?

Okay, I have found it.
In forcer to work mailchannels needs the MX record to be set correctly, which make sense but I had totally forget about that.