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.