Why do my email messages appear to fail when they really don't?

This is a common occurrence in the world of email if you have a mail program that lets you track delivery and or whether messages have been opened. Some apps call it "delivery receipt" or "return receipt", for example, but they all suffer from the same basic design flaw: every email program has to have the same feature implemented the same way for it to be useful, and, well, they don't.

Imagine: every time I send out an email message my mailer automatically includes a special mail header that asks their email program to send back a quick acknowledgment once your message is successfully delivered to the recipients mailbox. Now think "spam" and you'll immediately see why this is a really bad idea. Quantifying delivery data for members of a very large mailing list is the holy grail for spammers and they'd love a feature like this, so most modern servers simply ignore the request.

Even if that weren't the case, it's interesting to Google email header return receipt and see that there's even more than one commonly used email header to accomplish this task. Some talk about "Return-Receipt-Request:" while others talk about "Return-Receipt-To:". If you have the latter, it implies the former, and if you just have the former, it implies that the receipt-to would be the sender. Ah, another lack of standardization problem.

The problem gets even worse when you talk about tracking opening of messages because, after all, getting a message into a mailbox doesn't mean anyone is ever going to actually open it and read the contents. Again, though, spammers have ruined any utility for this sort of capability because if they could indeed identify which 2% of their five-million-address list actually open up the junk they send out, they could quickly winnow their massive dead list down into a small, valuable sublist to whom they would then send 100x the number of messages they already disseminate.

Finally, think of how much email is already flowing back and forth on the wires. Now multiply that all by two simply so we can all know if messages are delivered / opened. I think that it would quite measurably impact Internet traffic patterns and, in a sort of digital Heisenberg Uncertainty Principle way [ref], having those delivery receipts widely implemented would make mail just a bit less likely to be delivered quickly and accurately.

My advice to you: turn off this feature in your email and trust that the system is working if you don't get a bounce notice within a few hours of sending a message.

If, on the other hand, the problem is that you're receiving incessant "delivery failed" notification messages from sendmail even though your recipients are reporting that they do receive your messages, then you should talk to the administrator of the mail server you use: something's set up wrong, they have a bad DNS server that's failing out, or something else is wonky. Once in a blue moon getting a spurious delay or failure message is no big deal, but if it's a daily occurrence...