Domain database url MTA option

Memcache/Redis MTA options:  (memcache:/redis: URL)
The value of the  MTA option should be either a  memcache: URL or (as of MS 8.1) a redis: URL for storing  domain database data (that is, supplementary rewrite rules).

See also:
 * Domain database
 * Database MTA options
 * Rewrite rules
 * Domain database
 * MTA URL types
 * Memcache MTA options
 * Redis MTA options