Enable use of dns databases Tune with confMAPDEF
DNS stands for the Domain Name System protocol. DNS provides access to information about hostnames and addresses. DNS is covered fully in Chapter 9 on page 321.
This DNSMAP compile-time macro, when defined with V8.12 sendmail and above, allows you to look up host and address information inside your configuration file using the dns database map type (dns on page 905). You enable the dns database map type in your Build m4 file like this:
This definition will silently fail if you do not also define NAMED_BIND (NAMED_BIND on page 124) to include general DNS support inside sendmail. Normally, NAMED_BIND is defined by default, so that should not be a problem.
If you wish to use the enhdnsbl feature (FEATURE(enhdnsbl) on page 263) for improved spam screening, you must define this DNSMAP compile-time macro when building sendmail.
If you are running a precompiled
sendmail binary, you can use
debugging command-line switch (-d0.1 on page 542) to determine whether DNSMAP support
is included (if it appears in the list, support is