BehaviorOnMxFailure
The action that you want Amazon Pinpoint to take if it can't read the required MX record for a custom MAIL FROM domain. When you set this value to UseDefaultValue, Amazon Pinpoint uses amazonses.com as the MAIL FROM domain. When you set this value to RejectMessage, Amazon Pinpoint returns a MailFromDomainNotVerified error, and doesn't attempt to deliver the email.
These behaviors are taken when the custom MAIL FROM domain configuration is in the Pending, Failed, and TemporaryFailure states.