> I cannot imagine any technical or policy reason for leaving that field blank. > It has Omission written all over it.
> This problem affects multiple shops. If should be fixed at the source. The latest revision of the SMTP RFCs (RFC 5821) do address this issue somewhat, to wit: 4.5.5 Messages with a Null Reverse-Path There are several types of notification messages that are required by existing and proposed Standards to be sent with a null reverse-path, namely non-delivery notifications as discussed in Section 3.7, other kinds of Delivery Status Notifications (DSNs, RFC 3461 [32]), and Message Disposition Notifications (MDNs, RFC 3798 [37]). All of these kinds of messages are notifications about a previous message, and they are sent to the reverse-path of the previous mail message. (If the delivery of such a notification message fails, that usually indicates a problem with the mail system of the host to which the notification message is addressed. For this reason, at some hosts the MTA is set up to forward such failed notification messages to someone who is able to fix problems with the mail system, e.g., via the postmaster alias.) All other types of messages (i.e., any message which is not required by a Standards-Track RFC to have a null reverse-path) SHOULD be sent with a valid, non-null reverse-path. Implementers of automated email processors should be careful to make sure that the various kinds of messages with a null reverse-path are handled correctly. so it comes down to handling of failed non-delivery notifications to prevent mail loops as the primary reasons to permit null paths. Excluding all null reverse paths breaks an important function of the underlying protocol, but the sheer scale of the Internet makes it difficult to implement anything quickly. (Note that none of the IBM supported implementations (other than sendmail) support any of this -- just our small part of the world doesn't handle this, so expecting the larger universe to conform to us is unlikely. The fact that email works at all after 30+ years is a pretty impressive display of backward compatibility.) ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
