If you are using secondary domains for creating sending accounts, it's recommended to set up forwarding to your main domain (website).
Follow the steps in this video to set up your forwarding:
Log in to your GoDaddy.
Go to your domain list .
Find the domain that you want to redirect and click on the small three dots. Click Manage DNS
Scroll down to the Forwarding section
Click Add Forwarding
Choose http:// or https:// and enter the main domain that you want to be the destination. Select Permanent as Forward type and Save the changes.
And you are all set!