A recent service incident with email provided a reminder to me that email delivery is not guaranteed for message delivery. In the incident, the sender was using email to deliver a specific 1-to-1 message. It was not a marketing campaign. Since the distribution list was large, they chose to send the emails in batch through a provider. The problem was that some of the recipients never received the email message even though the ESP stats showed 100% delivery rate.
There are multiple factors that affect email delivery and some of them are out of the control of the sender. The sender can control attributes such as subject and message content but they can’t completely control what happens after the email is handed to an ESP on behalf of the recipient. From that point there are spam/bulk mail rules at the ESP as well as personalized mailbox rules for the recipient that affect the message delivery.
By chance, I was registering for Peachtree Road Race (10K) which requires a lottery for registration. I noticed the following statement on their explanation of how runners would be notified of the lottery results.
Email is efficient, fast, and low cost. But email delivery is not guaranteed. So when we use email to deliver specific B2C or B2B messages that require some type of acknowledgement, it’s a good idea to augment the message with another form of message delivery such as a postal mail piece or electronic posting on a web site.