Dotmailer provides two options that you can choose from in order to have a custom domain with them:
Purchase one through dotmailer for them to manage
Delegate a domain or subdomain to dotmailer for them to manage
Once any of the above is done, dotmailer takes the responsibility of managing your domain and the emails for you. They also take responsibility for authenticating your email with SPF and DKIM.
To learn more about the options and how dotmailer manages and handles your mail please click on the button below.