> > I see no Return-Path headers in some IETF traffic, including > > <[EMAIL PROTECTED]> as it appears in my mailbox. > > Instead I see an old UNIX-style From_. > > That's because Return-Path: is frequently added at final delivery. My > MTA adds that, some other don't. (Many Unix MTAs use the From_ line).
Note that the ones that don't add return-path are in violation of over 20+ years of mail specificatons. See RFC 821 (top of page 22), RFC 1123 (section 5.3.3 among others), and RFC 2821 (section 4.4). However there's no guarantee that Return-Path is either consistent for all messages sent to a list, nor that it is uniquely associated with a list. The few standards that apply to lists only require that the return-path address serves the purpose of informing the list maintainer (perhaps a robot) of nondelivery reports. Keith
