sendmail, 4th Edition

dns

Look up addresses using DNS V8.12 and later

The dns type is an internal database map available to perform DNS lookups. It is declared like this:

Kdnslookup dns -Rlookup-type

The -R switch—which specifies the DNS query to perform—must always be included. Table 23-11 shows the DNS queries that are supported.

Table 23-11. The dns database-map type -R switch query values

-R Value	Means
A	Return IPv4 address records for the host (RFC1035).
AAAA	Return IPv6 address records for the host (RFC1886).
AFSDB	Return an AFS server resource record (RFC1183).
CNAME	Return the canonical name for the host (RFC1035).
MX	Return a best MX record for the host (RFC1035).
NS	Return a name server record (RFC1035).
PTR	Return the hostname that corresponds to an IP record (RFC1035).
SRV	Return the port to use for a service (RFC2782).
TXT	Return general (human-readable) information (RFC1035).

If an -R value other than those in Table 23-11 is specified, the following two errors are printed and logged. If the -R switch is omitted, only the second error is printed and logged:

configfile: line num: dns map lookup: wrong type bad -R value
configfile: line num: dns map lookup: missing -R type

To make this dns database-map type more useful, the switches shown in Table 23-12 are also available for your use.

Table 23-12. The dns database-map type K command switches

Switch	§	Description
-A	-A on page 886	Append values for duplicate keys.
-a	-a on page 887	Append tag on successful match.
-B