Sieve subaddress extension

The MTA supports the Sieve subaddress extension specified in RFC 3598 (Sieve Email Filtering -- Subaddress Extension). The capability string is " ": require "subaddress"; The subaddress extension adds support for keywords " " (the local-part minus the subaddress) and " " (the subaddress itself) to the address test and, if the envelope extension has also been enabled, to envelope tests.

Note that configuration of what character the MTA interprets as the separator between the username and their subaddress is controlled by the  MTA option (by default, the plus character,  ); background on other aspects of the MTA&#x27;s subaddress handling can be found in the discussion of   and related channel options.

Use of subaddresses on an email address, whether when subscribing to mailing lists, or for  list moderator purposes, or for special purpose message forwarding, can make specialized handling of particular sorts of messages much more convenient. In reaction to the presence of a subaddress, a user&#x27;s Sieve script might: deliver the message directly into a folder  (use " "),  generate an alert notification  (use " "),  perform particular forwarding (use " "), etc.  For instance, suppose a user has subscribed to a mailing list using the subaddress. Then the following Sieve script: require &#x5b;"envelope","subaddress","fileinto"&#x5d;; if envelope :detail "to" "game-list" { fileinto "games"; } would cause messages addressed to the user due to their membership of that list to get filed into the folder named " ".

See also:
 * subaddressexact Option
 * subaddress_char MTA Option
 * Sieve address test
 * Sieve envelope extension
 * Special address formats for list members
 * Moderated mailing lists
 * Sieve supported extensions