Reverse url MTA option

Direct LDAP usergroup lookup MTA options:  (URL)
The  MTA option specifies the URL to query for address reversal and associated side-effects. Standard LDAP URL syntax as per RFC 2255 is used, except that the LDAP server and port may be omitted (in which case they are specified by the   and   MTA options -- or in legacy configuration, alternatively specified via the configutil parameters   and  ). Also, certain substitution sequences are available. The length, before substitution, is limited to 256 characters; (the limit was 252 characters in iMS 5.2 and earlier); the length resulting from the substitutions is limited to 1024 characters.

For typical MTA configurations, the usual value to which to set the  MTA option is " ". Indeed, as of 7.0.5, this is the default; (previously there was no default and a value had to be set explicitly).

Note that the   substitution  sequence, which is the filter for the LDAP query, uses the attributes named by the    MTA option, (or if that option is not set in legacy configutation, the attributes named by the   configutil parameter).

The reason that  normally is set to use  a filter that searches on the canonical   attribute, as well as the "subject to reversal" attributes such as , is that    lookups actually do more than pure address reversal:   lookups also result in  setting other possibly desired information for messages, including for instance use of attributes named by the   ,   , and    MTA options. Therefore, the canonical  attribute is included in the search filter (included in   which controls what is included in the filter referred to via the    substitution sequence) so that lookups will succeed, and find desired information, even for those users whose addresses are already in canonical form.

See also:
 * Direct LDAP usergroup lookup MTA options
 * Overview of Direct LDAP configuration
 * LDAP lookups for address reversal
 * Alias and address MTA options
 * LDAP URL substitution sequences
 * Intended side effects of LDAP address reversal
 * ldap_port MTA Option
 * ldap_host MTA Option
 * ldap_mail_aliases MTA Option