Domain match cache size, domain match cache timeout MTA option

Domain match cache control
As of MS 6.0, the  MTA option (as well as the    MTA option) is mostly irrelevant, since as of MS 6.0 there is an underlying domain map cache of domains. That is, the underlying domain lookup code used by the MTA as well as other Messaging Server components now maintains a (large) cache of lookup results; see the   MTA option for a discussion of the timeout on the underlying domain lookup cache entries. The MTA&#x27;s own private-to-the-MTA cache has thus become mostly redundant -- it&#x27;s a cache in front of a cache (though its entries are smaller in the case of negative matches, so potentially if one was especially concerned about optimizing the case of caching of large numbers of negative matches, the MTA&#x27;s private cache might be slightly useful).

The  options control some performance tuning formerly (in iMS 5.2) relevant  when operating in direct LDAP mode, in particular when a rewrite rule with a   in the template is being used. When such  domain map lookups are performed, the results can be cached by the MTA (apart and in addition to the  caching done by the underlying domain map LDAP lookup code); that is, an in memory cache is maintained by the MTA of the results of "recent" such lookups. The    MTA option, which defaults to 100000, controls how many results are cached. The   MTA option, which defaults to 600, specifies how long in seconds to maintain cache results. But note that all that&#x27;s being cached here by the MTA is whether or not the domain is "local", (that is, in the DIT). The actual values of attributes, such as, is cached in the underlying domain map code; see the    MTA option for a discussion of the timeout for that underlying cache.

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:
 * Direct LDAP domain lookup MTA options
 * Domain LDAP lookup rewrites
 * LDAP lookup cache MTA options
 * ldap_domain_timeout Option