Another standard feature missing in Opera's built-in mail client is support for read receipts.
In other clients, here's how it works:
When you send a message, you have the option to request that the recipient sends you a read receipt so that you know they got the message and read it.
In the outgoing message, all that's added is a "Disposition-Notification-To" header that has the same value as the "From" header. The recipient's client will detect this header and ask the recipient if he wants to send a receipt message to you confirming that he read the message.
If the recipient chooses yes, the client will send back to you a "multipart/report; report-type=disposition-notification;" message with the subject of the received message prefixed by "Return Receipt (foo) – " where foo is "displayed" or "deleted" for example.
The receipt message consists of 3 parts:
- A text/plain part mentioning that the message is a return receipt.
- A message/disposition-notification part that contains UA info specified via the Reporting-UA, Final-Recipient, Original-Message-ID and Disposition headers.
- A text/rfc822-headers part that contains the headers of the message you sent to the recipient.
Then, when you get this message back, your client displays the parts of the receipt message.
Opera doesn't support any of this.
This is basically all covered by RFC5337. But, Opera only needs to support what other mail clients support.
However, note that many Opera users are against this because:
- This whole thing breaks if the recipient refuses to send a read receipt. And, most recipients do refuse to send a receipt.
- The sender can always just say "let me know if you get this", which has the same chance of getting a result as a read receipt. So, why have a complex request and confirm feature that does the same as simple text?
- A read receipt request is less personal than "Let me know if you get this" to the point that the request is offensive to many users.
- This breaks if the recipient's client doesn't support read receipts while the "let me know if you get this" text will have a chance to work in any client.
But, with that said, many senders *rely* on read receipts and are lucky enough to have recipients that play along. And, the senders don't like to mix "let me know if you get this" with the content of their messages. Given that, it's something that the developers of other mail clients felt was a required feature.