Includefinal, suppressfinal, useintermediate Channel Options

From MsgServerDocWiki

Including altered addresses in notification messages (includefinal, suppressfinal, useintermediate)

When the MTA generates a notification message (bounce message, delivery receipt message, etc.), there may be several forms of an address available to the MTA: the preserved "original" form of a recipient address (the ORCPT form---in principle, that form originally typed by the sending user, but in practice that true original form may not have been preserved and instead some "later", transformed version may be the earliest form preserved), the "recently" active form (referred to here as the "intermediate" form) corresponding to the form of the address prior to any most recent forwarding applied by the MTA, and an altered "final" form of that recipient address (as for instance a final form after forwarding is applied). The MTA always includes the original form (assuming it is present) in the notification message, since that is the form that the recipient of the notification message (the sender of the original message which the notification message concerns) is most likely to recognize. The includefinal, suppressfinal, and useintermediate channel options control whether the MTA also includes the intermediate or final form of the address. includefinal means to include the final form of the recipient address; useintermediate is the default, and means to include the intermediate address form rather than the final address form; suppressfinal causes the MTA to suppress the final and intermediate address forms, if an original address form is present, from notification messages. Including the intermediate form is normally useful, especially to the postmaster of the MTA system itself, as the original address form, while presumably recognizable to the original sending user, may bear no obvious relationship to the form of address active by the time the MTA processed the message; in order to figure out what recipient on the MTA system was intended, something like the intermediate or even final address form may well be necessary. Suppressing the inclusion of any final or intermediate form of address entirely may be of interest to sites that are "hiding" their internal mailbox names from external view; such sites may prefer that only the original, "external" form of address be included in notification messages.

Note that only some channels fully support the useintermediate channel option; for other channels (including all channels written using the API) , the effect of useintermediate is merely to use the final address form, that is, it is effectively equivalent to includefinal.