If you remove a custom domain, your end users will no longer be able to access applications or other resources using the custom domain name. If you remove a trusted email domain, you will no longer be able to send email messages from the trusted domain.
  1. Go to Settings > Domains.
  2. Locate the custom domain or trusted email domain that you want to remove.
  3. For the appropriate entry, click Remove.
  4. In the confirmation message, click Remove.