I have added a custom domain (woodnott.com), which seems to be working if I ignore the security warning in Firefox. See below for the error:
*Web sites prove their identity via certificates. Firefox does not trust this site because it uses a certificate that is not valid for www.woodnott.com. The certificate is only valid for the following names: .netlify.app, netlify.app Error code: SSL_ERROR_BAD_CERT_DOMAIN
Looks like the A Record is configured incorrectly:
host woodnott.com
woodnott.com mail is handled by 10 eforward1.registrar-servers.com.
woodnott.com mail is handled by 10 eforward2.registrar-servers.com.
woodnott.com mail is handled by 10 eforward3.registrar-servers.com.
woodnott.com mail is handled by 15 eforward4.registrar-servers.com.
woodnott.com mail is handled by 20 eforward5.registrar-servers.com.