Use auth return, use canonical return, use orig return MTA options

Return address type used in checks MTA options:, ,
The MTA maintains three different forms of the envelope From address: the original from the MAIL FROM SMTP command (or its equivalent in other protocols), one that has had address reversal applied, and one that has been fully canonicalized, which includes mapping of    attribute matches to the corresponding    attribute value. Additionally, there may be an address produced as a result of an authentication operation that has similar semantics.

There are many places where the MTA performs comparisons against or constructs mapping probes containing the "return" address. But since there are multiple "return" addresses, there needs to be a way to select the one that is used. This is controlled by the,  , and   MTA options. Each of these options accepts a bit-encoded integer argument, with each bit controlling a particular place where a "return" address is used.

If the bit in  is set and an authenticated address is available, it is used and the corresponding bits in the other options become no-ops. If the bit in  is set (and the one in   is clear), then the canonicalized envelope From address is used and the corresponding bit in   becomes a no-op. if the bit in  is set (and the ones in the other two options are clear) then the original envelope from address is used. Finally, if none of the bits are set, the envelope From address that has had address reversal applied is used.

The  MTA option was added in 7.0;   is first available in 6.3.

The uses of the return address the various bits control are described in the following table:

The default for  and   is 0. The default for  is 0 prior to 7.2-7.02; in 7.2-7.02 and later it is 2097152, which preserves the existing default of using the original envelope From access in the    mapping. Also note that setting bit 21 in  makes no sense as the authenticated sender address is available as a separate field in the probe.

See also:
 * Address reversal
 * ldap_equivalence_addresses MTA Option
 * ldap_primary_address MTA Option
 * Alias and address MTA options
 * Recipient access mapping tables
 * Recipient access mapping tables
 * Recipient access mapping tables
 * Recipient access mapping tables
 * Alias file named parameters
 * alias_auth_list Option
 * alias_moderator_list Option
 * alias_sasl_auth_list Option
 * alias_sasl_moderator_list Option
 * alias_cant_list Option
 * alias_sasl_cant_list Option
 * alias_auth_mapping Option
 * alias_moderator_mapping Option
 * alias_sasl_auth_mapping Option
 * alias_sasl_moderator_mapping Option
 * alias_cant_mapping Option
 * alias_sasl_cant_mapping Option
 * alias_originator_reply Option
 * alias_deferred_list Option
 * alias_direct_list Option
 * alias_hold_list Option
 * alias_nohold_list Option
 * alias_deferred_mapping Option
 * alias_direct_mapping Option
 * alias_hold_mapping Option
 * alias_nohold_mapping Option
 * ldap_auth_domain MTA Option
 * ldap_cant_domain MTA Option
 * ldap_auth_url MTA Option
 * ldap_cant_url MTA Option
 * ldap_moderator_url MTA Option
 * ldap_domain_attr_catchall_mapping MTA Option
 * Forward database
 * FORWARD mapping table
 * FROM_ACCESS mapping table