const _failedDeliveryFailure
const _failedTemplateError
const _networkServerIssues
const _skippedDueToPreviousHardBounce
const _mailProtocolIssues
const _mailboxNotAcceptingMessages
const _invalidSenderAddress
const _messageExceedsSizeLengthLimits
const _failedInvalidAddress
const _unsubscribedByFeedbackLoop
const _failedUnexpectedError