Mutation.addEmailDomain
Register a sending domain (DKIM selector defaults to em1).
ReturnsEmailSenderDomain!
Signature
Register a sending domain (DKIM selector defaults to em1).
store_idID!domainString!dkimSelectorString

Register a sending domain (DKIM selector defaults to em1).
Register a sending domain (DKIM selector defaults to em1).
store_idID!domainString!dkimSelectorString