At 14:08 09/17/2004 Friday, Fitzmaurice, Frank CIV OGC wrote:
 >I posted the original message in this thread. What I am looking for is
 >notification when a subscriber does not receive a message (permanent
 >error). We need to investigate each case since this a distribution list
 >and it is critical that all parties receive the announcements. What I am
 >trying to avoid are messages short of a complete delivery failure to cut
 >down on work load. Does Listserv attempt to resend a message if it gets an
 >initial failure?

This very much assumes that the mail and listserv infrastructure has some
sort of guaranteed delivery, and/or guaranteed notification if not delivered.

None such exist.

Furthermore, due in part to the email infrastructure, the delivery of
"bits" to a mail server is not proof that the subscriber has received such.

More to the point:

1) LISTSERV is not a mail transmission protocol (though SMTP is)

2) SMTP clients and servers do have retry capabilities but these appear
in practice not to be consistent across all implementations; this is
"best effort" but sometimes "best" is not good enough

3) anti-spam filters sometimes cause false positives and may not send it
back to any RFC821 or 822 addresses but instead just toss them away

etc.