Alias entry cache * MTA options

LDAP and URL lookup cache options:  (0 or 1),   (integer),    (integer)
The  MTA options control some performance tuning relevant when operating in direct LDAP mode, in particular when   options are being used. When  lookups are performed, the results can be cached; that is, an in memory cache is maintained of the results of "recent" such lookups. The  option, which defaults to 1000, controls how many results are cached. The  option, which defaults to 600, controls how long in seconds to maintain cache results. The  option, which takes a boolean argument and defaults to 0 (false), controls whether or not negative results (that is, failures to find an alias) are cached.

There is a trade-off between performance on the one hand, vs. memory usage and speed with which changes to the LDAP entries take effect on the other hand.

See also:
 * LDAP lookup cache MTA options
 * alias_url0 MTA Option