I'm building an app where each customer can have their own subdomain. For this example, he setup his subdomain to be: whisky
I created a wildcard subdomain in my DNS: *.myapp.com A 18.104.22.168
So when he accesses my webapp, he would use the url: whisky.myapp.com and it would resolve to 22.214.171.124.
My app also sends email (email will be handled by sendgrid) using the same subdomain my customer chooses: e.g. firstname.lastname@example.org
But when I tried to setup a wildcard MX record to sendgrid's servers, my DNS provider does not allow me to do so, citing some standards violation.
e.g. *.myapp.com MX sendgrid.com
Is there any way I can have wildcard subdomains for both?