AlanFortney said:
I forgot to mention, a Delivery Receipt is always returned, but a Read
Receipt is not.
A delivery receipt is NOT a read receipt.
A delivery receipt is the receiving mail host sending back an
acknowledgement e-mail. The e-mail may not even get delivered to the
recipient's mailbox due to spam filtering. The recipient may not see it
do to user-defined server-side or client-side filtering (spam or rules).
You won't ever know if the recipient got your e-mail when using the
delivery receipt. You only know the recipient's mail host got your
e-mail. Most mail host don't bother sending a delivery receipt. They
already provide negative feedback via NDRs (non-delivery reports)
e-mails if the received e-mail is undeliverable - and only send those if
they accept an e-mail before determining if it is actually deliverable
(a good mail host will reject an undeliverable e-mail during the mail
session with the sending mail host, so the sending mail host tells its
sender account that their e-mail was undeliverable). Mail hosts don't
need to double their feedback volume by sending back positive feedback
that e-mails were received by the mail host (DSNs) as they already send
back negative feedback for undeliverable e-mails (NDRs). When all
parties to an e-mail are using the same mail server, like Exchange,
there is no point in asking for a delivery receipt. After all, your
sending mail host is the same as their receiving mail host, so if your
mail host accepts your e-mail then you already know it got accepted by
the recipient's mail host (because it's the same one that you use).
Delivery receipts are just that: asking for acknowledgement that your
e-mail got to the recipient's mail *server*.
A read receipt is the recipient's e-mail client sending back an
acknowledgement e-mail. Users can configure their e-mail clients to
always send, prompt, or never send acknowledgements. I believe the
default is to Prompt. Eventually the user grows tires of the prompts
and always answering No that they configure their e-mail client to never
send the acknowledgements (and also never be bothered with any prompts
about read receipt requests that they want to ignore). Read receipts
are just that: asking the user's e-mail *client* to acknowledge that the
recipient *opened* your e-mail.
Summary:
- The delivery receipt header (Return-Receipt-To) is a request to the
receiving mail server that it send a DSN (delivery status notification)
as soon as it accepts the email. No DSN is required if the mail server
rejects the mail session for a non-deliverable e-mail (the sending mail
server will report back the bad mail session status).
- The read receipt header (Disposition-Notification-To) is a request
that the recipient's email client send back a DSN after the recipient
opens the e-mail.
Because there is no guaranteed delivery for e-mail, the same holds true
for DSN e-mails sent for delivery receipts or read receipts.
You never bothered to mention what mail server you are using. If
Exchange, contact its admin to find out how the 3 accounts differ from
the 6 accounts. Could be some accounts are "outside" the Exchange
organization or those use an SMTP connector to Exchange. It is possible
the Exchange server is configured to strip some headers from external
inbound e-mail sources or for outbound e-mails outside the Exchange
server. Same stripping could occur with anti-spam software or anything
else that interrogates the user's e-mail traffic.
