SproutDNS

I wrote last year about using “stunt” nameservers for customer subdomain authentication – i.e. dynamically generating all the authentication records needed in DNS for each customer as needed. For example, if you’re an ESP that has customers who can’t or won’t use their own domains and you still need to give them unique subdomains you can generate CNAME records to support white label DKIM authentication: selector ._domainkey. customerid .espcustomer.com CNAME selector .dkim.esp.com or generate white label DMARC with useful rua= reporting: _dmarc. customerid .espcustomer.com TXT “v=DMARC1 p=none rua=rua+ customerid @esp.com” Once you’ve set up these DNS records once they’ll work for all your customers, you just need to put the right domains in your DKIM signature and return path. I shared some demo code to explain the concept last year, but since then we’ve developed a robust, production-ready application to dynamically serve DNS in this way. It’s called