Message Disposition Notifications (MDN) are email reports sent by the MTA to a sender and/or postmaster reporting on a message’s delivery disposition. For example, if a message is rejected by a Sieve filter, an MDN will be sent to the sender. MDNs are also known as read receipts, acknowledgements, receipt notifications, or delivery receipts. The Sieve scripting language is typically used for messaging filtering and vacation messages.
The instructions for modifying and localizing MDNs parallel those described in customizing and localizing delivery status notification messages with some minor differences as described here. (See 10.10.2 To Customize and Localize Delivery Status Notification Messages and 10.10.3 Internationalization of Generated Notices.
The mapping (called the DISPOSITION_LANGUAGE mapping) parallels the notification_language mapping table (see 10.10.2 To Customize and Localize Delivery Status Notification Messages) used to internationalize status notifications.
However, probes for MDNs to this mapping take the following form:
type is disposition type, which can be one of the following: displayed, dispatched, processed, deleted, denied, or failed.
modifiers is a comma-separate list of disposition modifiers. The current list is: error, warning, superseded, and expired.
source-channel is the source channel producing the MDN.
header-language is the language specified in one of the following: accept-language, preferred-language, or x-accept-language. (MTA uses the first of these options that is present.)
return is the address to which the notification is being returned.
recipient is the address that the disposition is about.
The result of the disposition mapping consists of two or three pieces of information separated by vertical bars (|). The first piece of information is the directory where the template files for the disposition notification can be found. The second piece of information is the character set into which the standalone disposition text should be forced. (This information is required because some dispositions—notably the dispositions produced by autoreply echo or the use of the :mime parameter to the vacation Sieve action—do not employ template files and consequently cannot inherit the character set from those files.) Finally, the third piece of information is an override subject line for the notification. This information is only used if the $T flag is also set by the mapping.
The following additional template files are used to construct MDNs:
disposition_deleted.txt disposition_failed.txtdisposition_denied.txt disposition_prefix.txtdisposition_dispatched.txt disposition_processed.txtdisposition_displayed.txt disposition_suffix.txtdisposition_option.opt
The use of these template files parallels that of the various return_*.txt files for status notification messages. Message text for *.txt files should be limited to 78 characters per line.