I’m bumping into a very strange issue. I want a subdomain of adsb.mydomain.com as an A record, but whenever I try and set that, I get an error with a blank message. I have tried with all the domains hosted on my instance and they all do the exact same thing. What’s going on here…?
Add an email user account with the name in the format of user@adsb.mydomain.com. That should work for you. Change the IP by adding an A record on the Custom DNS page (which is probably what you are trying to do now) to the correct IP for that subdomain.
For the record - the above is a workaround. I am unable to reproduce your issue.