Alias urlN MTA options

Alias and address reversal MTA options:  (URL)
The  MTA options each specify a URL to query for alias lookups. If more than one of these options is set, then the URLs lookups specified are performed in the order specified by the   MTA option. The options are normally checked in numeric order, so, if specified, will be the first URL queried. Note that with the usual value of  (8764),  the   option is not used.

Such alias lookups will be performed any time an envelope To address matches the local ("l") channel, or any channel marked with the   channel option.

The URL (that is, the  option value) must be specified using standard LDAP URL syntax as per RFC 4516, with the following exception and special interpretations:



 The LDAP server and port are typically omitted, being instead specified via the  and   MTA options; (or if the MTA options are not explicitly set, the MTA will use more general options: in legacy configuration, the configutil parameters   and , or in Unified Configuration the    and   base options). (Indeed, prior to Messaging Server 7.4-18.01, the host and port had to be omitted; but as of Messaging Server 7.4-18.01, specifying the host and port in the URL itself is supported.) 

 The MTA makes a distinction between a completely omitted attributes field, which as per RFC 2255 means to request the return of all attributes, and an attributes field consisting of the asterisk character,, which the MTA instead interprets as meaning to request the return of all known-to-the-MTA attributes, that is, all the attributes listed in Table of MTA LDAP attribute name options. This distinction is available since for some directory setups, there may be a noticeable performance difference in LDAP directory response to one type of query (all attributes requested) vs. the other type of query (specific, though large, list of attributes requested). 

 Various substitution sequences  of the form " " are available. A literal dollar sign must be represented by " ". 



The LDAP URL, before any substitutions, is limited to 256 characters in length (252 in iMS 5.2 and earlier); the substitutions may insert additional material and the length after such substitutions is limited to 1024 characters. Note that the substitution of known attributes when asterisk,, is specified as the attribute to return, is not considered as part of the regular substitution; this substitution is performed at a later step and the length after this "known" attributes substitution is limited to 4096 characters.

, if set, is normally looked up first (unless the  value has been changed). Next, if set, etc. It is permissible to have "gaps" in the  list; for instance, it is permissible to set   and   without setting.

Since  is normally looked up first, in a typical direct LDAP configuration it is used to perform the "main" user/group lookup, with   optionally being used by those sites that need to do an additional, secondary lookup. In particular,  is typically used by those sites that need to support vanity domains, or it could be used by sites that do not support vanity domains but that need to support "old-style" catch-all addresses, (that is, sites that use the deprecated approach of defining a catch-all address by means of a user    attribute with a wildcard, rather than using the preferred approach of defining a domain level    attribute).

As of 7.0.5, the default value for  is. Previously, there was no default and   had to be set explicitly. The other  MTA options have no default value.

See also:
 * Direct LDAP usergroup lookup MTA options
 * Overview of Direct LDAP configuration
 * Alias and address MTA options
 * alias_magic MTA Option
 * aliaslocal Option
 * ugldaphost Option
 * ugldapport Option
 * LDAP URL substitution sequences
 * Aliases in LDAP
 * ldap_alias_addresses MTA Option
 * ldap_domain_attr_catchall_address MTA Option