wizkkidd

   When deployed alone (i.e. without a DANE record, and using Web PKI
   for certificate verification), SMTP STS offers the following
   disadvantages compared to DANE:

   o  Infrastructure: DANE may be easier for some providers to deploy.
      In particular, for providers who already support DNSSEC, SMTP STS
      would additionally require they obtain a CA-signed x509
      certificate for the recipient domain.

   o  Security: DANE offers an advantage against policy-lookup DoS
      attacks; that is, while a DNSSEC-signed NX response to a DANE
      lookup authoritatively indicates the lack of a DANE record, such
      an option to authenticate policy non-existence does not exist when
      looking up a policy over plain DNS.