By setting up your own domain, the recipients will see your custom domain as the mailing´s sender address and as domain for all trackable links. This has the advantage that the email service provider is not visible at first glance. If you want to use your own custom domain in a account you need to update the name server of your domain. This involves changes in the DNS configuration, whereby the domain will refer to the system´s servers in the future. The DomainCheck checks the entered domain for a possible integration into a account.