BehaviorOnMxFailure
The action to take if the required MX record can't be found when you send an email. When you set this value to UseDefaultValue, the mail is sent using amazonses.com as the MAIL FROM domain. When you set this value to RejectMessage, the Amazon SES API v2 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.