EC recognises DANE as standard for tendering
DANE has been recognised by the European Commission as an official standard for use in tendering, both in e-mail and on the web. To secure recognition, a standard has to be open, transparent, impartial and developed on the basis of consensus — the idea being to ensure technical interoperability across government bodies throughout the EU.
DANE for the web supplements (and is seen as the long-term successor to) the certificate system currently used by browsers ('key' icon). The flaws in that system and the need for an alternative have been highlighted by the DigiNotar debacle and other events.
Mail gateways don't use a certificate system. So, in e-mail, DANE is used to attach the STARTTLS server certificate and secure the STARTTLS option.
In both cases, DANE works through a DNSSEC-secured TLSA record containing a hash code for a particular certificate.
Mail server security standard SPF is covered by the EC decision as well. DNSSEC is strongly recommended for SPF, but not mandatory.