Allow CNAME chaining for tracking opens, clicks.
Currently my app (email.mydomain.com) CNAME is pointed to mailgun.org, but when I have my users' domains point to email.mydomain.com, it does not accept this as a chain CNAME.
It would be nice to validate this so it can be whitelabel.
Had the same issue. It's extra annoying because if Mailgun puts outs the tracking links, the will "just work", and it's only the validation system that is broken.