Keywords: addreturnpath, noaddreturnpath
Normally, adding the Return-path: header line is the responsibility of a channel performing a final delivery. But for some channels, like the ims-ms channel, it is more efficient for the MTA to add the Return-path: header rather than allowing the channel to perform add it. The addreturnpath keyword causes the MTA to add a Return-path: header when enqueuing to this channel.