Ensure your server is running an authentic copy of DirectAdmin
The main server IP might not be the same value that your domain resolves to. If you know the hostname of your server, this should resolve to the server's main IP. Also your spf TXT records should have the server IP listed in an ip4 field.
You can e-mail questions to sales@directadmin.com or send an inquiry by visiting the contacts page. We are available Monday through Friday, 9 AM - 5 PM Mountain Standard Time. You may also visit the forum to see if your question has been answered there.