Support DNS name resolution Tune with confENVDEF

The sendmail program automatically takes advantage of DNS lookups or MX records to resolve addresses and canonical hostnames. If your site is a UUCP-only site (or is otherwise not connected to the Internet) and does not run named(8) locally, you should probably disable NAMED_BIND:

                           disable DNS lookups

If you are running a precompiled sendmail binary, you can use the -d0.1 debugging command-line switch (-d0.1 on page 542) to determine whether NAMED_BIND support is included (if it appears in the list, support is included).

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