A new internet-draft is available from the IETF.
Abstract: «In much the same way one can track a parcel, this document proposes a simple method for returning the trace record of an e-mail to the SMTP originator (sender) as it passes through relays and gateways; passively, without the recipient’s intervention. Delays can thus be explained and important e-mails (or paranoid e-mailers) can rest knowing their message has at least arrived at its destination. »
«Much like parcel tracking, this is more of a gimmick than useful!»