Ldap domain attr smarthost MTA option

Direct LDAP attribute name MTA options:  (LDAP attribute name)
The  MTA option names the domain LDAP attribute, by default , used for routing of addresses in the domain but without a directory entry. That is, if a user address is not found in the directory, then route onwards, inserting the  value into the address as a source route.

Since the value of the  attribute (or whatever attribute is named by  ) will be used as a source route, note that that means that the actual routing of the address will depend on how the MTA has been configured to route such an address. In particular, best practice is to specify a FQDN (Fully Qualified Domain Name) as the value, since comprehensive configuration for proper routing of such domain names is part of normal MTA configuration. Use of less recommended substitutes, such as short-form hostnames or IP literal addresses, will only yield desired results if the MTA has been explicitly configured to route such substitute names appropriately.

See also:
 * Direct LDAP attribute name MTA options