Addreturnpath, noaddreturnpath Channel Options

From MsgServerDocWiki

Adding Return-path: header fields (addreturnpath, noaddreturnpath)

When specified a destination channel, the addreturnpath option causes the MTA to add a Return-Path: header line to all messages enqueued to the channel. noaddreturnpath disables this feature.

Note that the addition of a Return-Path: header line is usually a function of a final delivery agent (such as a final delivery channel). Most final delivery channels know to put a Return-Path: header on themselves. But for the convenience of some channels such as the ims-ms channel, where adding a Return-Path: header line in the channel program itself is not convenient, the MTA is also capable of adding the Return-Path: header itself if configured to do so via this channel option.

The addreturnpath MTA option is always considered to be set on the ims-ms channel; noaddreturnpath is the default for all other channels.