If you are using secondary domains for sending accounts, it's recommended to set up forwarding to your main domain (website). This way, when the clients enter your sending domain into a browser's address bar, they will be taken to your main website.
To set up the forwarding in Google, please follow these steps:
Log in to your Domains page and click on Manage
From the left-hand menu, select Website
Click on Forward domain
Enter the name of your primary site in the Website name field. Click on Advanced options
Select Permanent Redirect (301) for Redirect type
Under Path Forwarding, select Do not forward
In Forwarding over SSL, select SSL On - if you want to redirect to work for both HTTP and HTTPS requests
Confirm by clicking on Forward.
Learn more about scaling email outreach with secondary domains.