Intended side effects of LDAP address reversal

Doing a   lookup actually has  effects beyond pure address  reversal. (And this is why a   lookup normally uses the    substitution for a  filter that searches for a given  address as the canonical   attribute, as well as  searching for the attributes that would actually require address  reversal: one wants the   lookup to find an entry even for an  address that is already in canonical form.) The recommended setting for  the   MTA option  makes use of the LDAP URL    substitution to specify an extensive list of attributes to be fetched;  so   lookups also normally make use of (or at least fetch and  cache) the attributes named by the MTA options:

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</ul>

The recommended setting for the   MTA option also uses the    substitution for  locating the domain in which the  sending user address is located. Because of this implied lookup of the sending user&#x27;s domain, the MTA&#x27;s message processing can then also make use of  per-sending-domain LDAP attributes including those named by the MTA options:

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</ul>

Note: In actual operation, the MTA and domain map caching of domain         lookup results means that the domain attributes are often available          from a cache, without need for an additional actual LDAP query at          this point. That is, while the  caused  fetching of the sending user&#x27;s personal LDAP attributes is relatively likely to involve a query all the way to the backend LDAP server, the "fetching" of the sending user domain LDAP attributes is often short-circuited, with the domain attributes cached due to a prior lookup.

So the list of potential side-effects resulting from address reversal, when it is properly configured to fetch these various per-sending-user  and per-sending-domain LDAP attributes, is quite extensive, including  effects on message size limits, message recipient limits, conversion  tags, message capture, spam/virus filter processing opt-in, archiving  opt-in, source channel "switching", and (if a notification  message must be generated), notification language preference,  non-return-of-content in notification messages, and per-domain  postmaster address selection, etc.

New in the 8.0 release, bits of the  MTA option can be set  to disable use of either the envelope From (MAIL FROM) address, or the authenticated sender address, for purposes of source-based message size or recipient limit settings, as well as capture actions.

See also:
 * Address reversal
 * Subaddresses and address reversal
 * LDAP lookups for address reversal
 * reverse_url MTA Option
 * use_reverse_database MTA Option
 * usereversedatabase Option
 * LDAP URL substitution sequences
 * ldap_primary_address MTA Option
 * ldap_alias_addresses MTA Option
 * ldap_equivalence_addresses MTA Option
 * ldap_personal_name MTA Option
 * ldap_capture MTA Option
 * ldap_recipientlimit MTA Option
 * ldap_recipientcutoff MTA Option
 * ldap_sourceblocklimit MTA Option
 * ldap_preferred_language MTA Option
 * ldap_source_conversion_tag MTA Option
 * ldap_blocklimit MTA Option
 * ldap_source_channel MTA Option
 * ldap_source_optin1 MTA Option
 * ldap_preferred_country MTA Option
 * ldap_spare_1 MTA Option
 * ldap_domain_attr_report_address MTA Option
 * ldap_domain_attr_blocklimit MTA Option
 * ldap_domain_attr_recipientlimit MTA Option
 * ldap_domain_attr_recipientcutoff MTA Option
 * ldap_domain_attr_source_conversion_tag MTA Option
 * ldap_domain_attr_sourceblocklimit MTA Option
 * ldap_domain_attr_source_channel MTA Option