From: bruce@blilly.UUCP (Bruce Lilly)
Subject: Re: Return and read receipts (was Re: Return-Receipt-To & forwarding...)
Organization: Bruce Lilly
Date: Thu, 31 Dec 92 00:32:23 GMT
Reply-To: lilb@sony.compuserve.com (Bruce Lilly)

In article <1992Dec29.181814.4105@chance.gts.org> john@chance.gts.org (John R MacMillan) wrote:
>|> With return-receipt-to, a lack of response means nothing (your message
>|> may or may not have been delivered), and a positive response means
>|> there's a good chance your message was delivered, but it's my no means
>|> foolproof.
>|
>|The positive response tells me that there is a path to and from my
>|addressee.
>
>Lack of a bounce message tells you the same thing with about the same
>reliability ("pretty certain" vs. "fairly sure").  Yes there may be
>bizarre systems that don't generate bounce messages, but I don't think
>that's all that common anymore, and it's becoming less so. :-)

Lack of a bounce message tells me nothing useful:
	the message might have been delivered successfully to the
		intended destination
	the message might have been misdirected, and possibly
		delivered somewhere other than the intended
		destination
	the message may have fallen into a bottomless pit at a
		store-and-forward site
	delivery may have failed somewhere with a bounce message,
		but the bounce message may have been misdirected
		or lost or both
	several possible combinations of the above
	the message may be waiting at a store-and-forward site

	In summary, I have no positive indication that the message
	was delivered anywhere, and I have no indication that it
	wasn't delivered.

Receiving a bounce message tells me:
	some site somewhere might have failed to pass on the message
		(in fact, it may have forwarded the message)

A return receipt tells me:
	the message was delivered to a specific system (the one that
		sent the receipt), which attempted to perform final
		delivery
	(obviously) the system that sent the return receipt does
		acknowledge return-receipt-to
	the route taken by the original message and by the return
		receipt (via the Received headers)
	the amount of time elapsed between each hop of the original
		message and the return receipt (again via Received
		headers)
	[additional information might be obtained from the return
		receipt's Received headers, including: the MTA
		identity at each hop, the means of transfer between
		MTAs, changes to the envelope address]

	In summary, I know a) that the message went somewhere, b) where
	the message went, c) the route the message took, d) how long
	the message took to reach the place to which it went, e) that
	the MTA that sent a return receipt does in fact acknowledge
	return-receipt-to, f) the route taken by the return receipt,
	and g) how long the return receipt took to reach me.

If I have previously established that the MTA for a recipient acknowledges
return-receipt-to, and I do not receive a return receipt within a reasonable
time period, I know that something went awry or the MTA was changed.

>|  However, if I want some degree of proof that my
>|question reached Marshall Rose, it's a different story.
>
>  As "proof" your question reached mtr, a receipt is worthless;
>it's only an indication.  Another indication that your question
>reached him was that you didn't get a bounce message.  I feel that
>both these indications carry about the same weight.  If you get a
>significantly warmer and fuzzier feeling with the receipt I think
>you're just fooling yourself.

Isn't ``some degree of proof'' (the original wording, as you can see) the
same as ``an indication''?  In any event, failure to receive a bounce and
positive receipt of a return receipt clearly mean quite different things;
see above.

-- 
	Bruce Lilly		blilly!bruce@Broadcast.Sony.COM
					...uunet!sonyusa!sonyd1!blilly!bruce
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