MTA URL types

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A number of MTA options, channel options, alias options, etc., allow values of various URL types. Such URL types may include:

  • file: -- used to refer to files stored in the local filesystem
  • ldap: -- used to refer to data stored in the LDAP directory
  • ldaps: -- used to refer to data stored in the LDAP directory, accessed via LDAP+SSL
  • pabldap: -- used to refer to data stored in a Personal Addressbook LDAP directory
  • pabldaps:
  • extldap:
  • extldaps:
  • ssrd:
  • mailto:
  • data: -- URIs make it possible to specify data directly, in the URI itself
  • http:
  • imap: -- access data using IMAP. The credentials specified by the imap_username and imap_password MTA options are used to log in to the IMAP server and the URL is resolved with the URLFETCH IMAP command. Note that imap: URL resolution is part of the server-side support for the BURL SMTP extension (used to implement forwarding of messages without having to download them) so any usage of such URLs by the MTA must take into account the fact that there's only one set of such login credentials.
  • imaps: -- access data using IMAP+SSL.
  • metermaid:
  • memcache: -- new in MS 8.0
  • redis: -- new in MS

In addition, some such options may also support a non-URL form argument, assumed to be of an especially "appropriate" type for that option, depending upon the option. For instance, some options assume a file-path argument when no URL prefix is present, while other options might assume an e-mail address argument when no URL prefix is present.

Some MTA options, channel options, or alias options may allow use of certain substitution sequences in their value settings. The most general list of such substitution sequences may be found in the discussion of LDAP URL substitution sequences. However, some (but only some!) of these substitution sequences are also valid in other types of URL settings for certain MTA option or channel option or alias option settings. See discussion of specific options for details.

Note that in order to use as option values forms of URL that involve querying some external-to-the-MTA component, such as an LDAP URL, or the special "Personal Addressbook" (pabldap:) form of URL, or an IMAP (BURL) URL, or a MeterMaid URL, or a Memcache URL, typically configuration of just how the MTA should connect to that other component is necessary -- that is, configuration of just how to properly interpret such values is necessary. See MTA options such as the LDAP bind and connect MTA options, LDAP external directory lookup MTA options, LDAP PAB MTA options, BURL MTA options, Memcache MTA options, MeterMaid MTA options, or Redis MTA options for performing such configuration.

See also: