Have read through this topic and am feeling confused. The admin account can be whatever email address you use. It does not have to be set up through mailjet. Mailjet is just for outbound email from your forum.
I’d suggest you use your gmail or whatever email address you use every day and that you know will work to reach you. You will need to specify the email address you want to use when running /discourse setup or by editing /var/discourse/containers/app.yml.