What exact error code(s)/message(s) do you see, when you’re attempting to send?
It seems like your domain does not have that many DNS records, e.g. none for the website.
It also seems like you are pointing your MX record (which is inbound mail / receiving), towards the host name “ns1.siteground.net”, which based on the name, sounds to be incorrect.
What DNS record(s) did you get from your email provider?