
304 Part Two • IPv6 Protocols
intranet and internal mail systems, to avoid going through a security
firewall, or to provide a standard corporate address format (e.g.,
“firstname.lastname@example.com”) while allowing users to receive mail
at other addresses.
A number of RRs have been defined for use with DNS security exten-
sions; these include the SIG (security signature), KEY (security key), and
NXT (next domain) RRs defined in RFC 2535. Other special purpose RRs
include the NAPTR (naming authority pointer) type defined in RFCs 2168
and 2915 and the AAAA and A6 types defined for IPv6 address resolution;
there is even an RR defined simply for storing text