Enable inbound email receiving on a custom domain that has already been verified.Calling this endpoint stamps the domain as inbound-enabled and returns the inbound MX
record you must publish in your DNS. Once that MX record is detected in DNS during the
next verification check, AutoSend wires up the SES receipt rule and inbound becomes live
for the domain (at which point inboundDomainVerifiedAt is set).
ISO 8601 timestamp of when the inbound MX record was detected and the domain was
added to the SES receipt rule — i.e. inbound is verified and live. null until the
MX record is detected in DNS.