You'll need to have access to your domain's DNS records. The best way to find out if you can do this is to contact your domain name registrar or web hosting provider. You'll be adding what's called a new CNAME record to your DNS.
Step 1. Choose the domain name you plan on using
Choose the full domain name you will use when accessing this account e.g. eshot.yourdomain.com or email.yourdomain.co.uk or newsletter.yourdomain.net. The first part can be anything you want.
Step 2. Add the following CNAME record to the DNS for email
The CNAME Name should be the first part only of the domain name you plan on using. So for newsletter.yourdomain.net you would just enter 'newsletter' (without the apostrophes).
Please note: Some DNS servers may require you to add a period (.) after the address, so the CNAME Data would be "cname.createsend.com."
Step 3. Tell us
Once the CNAME record is in place, let us know what it is and we will verify it.
Alternatively you can send us a login to your domain control panel and we can do this for you.