Use forward database MTA option

Alias and address MTA options:  (bitmask)
The  MTA option controls whether or not the  MTA makes use of the forward database,  and also controls the exact format of  probes of the forward database and   mapping table. The value is a decimal integer representing a bit-encoded integer, the interpretation of which is  given in the table below.

Bit 0 is the least significant bit.

The default value for  is 0, which means that the  MTA will not use the forward database at all. Note that a   mapping table, if present, is always consulted.

See also:
 * Alias and address MTA options
 * Database MTA options
 * Forward database
 * FORWARD mapping table
 * ldap_domain_attr_catchall_mapping MTA Option