sendmail, 4th Edition

host

Internal table to store lookup hostnames V8.1 and later

The host database-map type is a special internal database used by sendmail to help resolve hostnames. It is fully described under the $[ and $] operators in $[ and $]: A Special Case on page 895.

Only a few database-map switches are available with the host type, and they are listed in Table 23-15.

Table 23-15. The host database-map type K command switches

Switch	§	Description
-a	-a on page 887	Append tag on successful match.
-d	Timeout.resolver (V8.10 and later)	The res_search() _res.retry interval (V8.12 and later).
-D	-D on page 887	Don’t use this database map if DeliveryMode=defer.
-m	-m on page 888	Suppress replacement on match.
-r	Timeout.resolver (V8.10 and later) on page 1108	The res_search() _res.retries limit (V8.12 and later)
-S	-S on page 890	Space replacement character.
-T	-T on page 890	Suffix to append on temporary failure.
-t	-t on page 891	Ignore temporary errors.

The -D database switch should probably always be used with this type on sites that have dial-on-demand connections to the Internet. It prevents host lookups when the DeliveryMode option (DeliveryMode on page 1004) is set to defer.