From: Cyrus Daboo (no email)
Date: Thu Mar 07 2002 - 14:14:46 EST
--On Thursday, March 7, 2002 10:49 AM -0600 Amos Gouaux
| tjk> Problem: Management wants a return receipt feature for emails.
| For what, read receipt or delivery receipt? For delivery receipt, I
| wonder if that's something lmtpd could do? Isn't read receipt
| something the mail client would do?
| Though, if delivery failed the message would be bounced, so the
| sender *should* know from that whether the message has been
There are two kinds of receipt in email that you can use:
1) Message Delivery Notification (MDN) - this consists of a set of headers
added to the message by the sender, indicating that they want notification
of when the message is processed (either read or deleted) by the recipient.
The recipients client is in charge of sending back the receipts. Clients
that support it usually have the option to turn it off, prompt before
sending, or automatically sending the receipt. It seems like the majority
of people turn it off!
2) Delivery Status Notification (DSN) - this consists of some optional
parameters added to the SMTP protocol exchange between the client and the
SMTP server. Clients can request DSN's for success, delay or failure, and
specify whether they want returned just the headers or the entire message
body as part of the receipt. In order for DSN's to work properly, each SMTP
server that handles the message enroute to delivery must support the DSN
extension, as these options are passed along with the message. Usually if a
DSN-aware server has to pass the message on to a non-DSN-aware server it
will send a receipt back to the sender stating that the message got that
far. A DSN success only guarantees that the message got delivered into the
recipients INBOX - it won't tell you anything about whether the recipient
actually sees the message. I think the DSN extension is pretty widely
deployed in SMTP servers so this ought to be a fairly reliable method,
though sometimes firewalls can get in the way.
-- Cyrus Daboo