Understanding Delivery Failures in Marketo
Today, let’s clarify some common misconceptions about email bounces, specifically the term "soft bounce," and dive into the details of Marketo’s retry algorithm.
Debunking the "Soft Bounce" Myth
Firstly, it's important to address a common term in email marketing: "soft bounce." This term is often used to describe temporary delivery issues, such as a recipient's inbox being full or their server being down. However, this terminology does not accurately reflect the realities of Simple Mail Transfer Protocol (SMTP), the standard for email transmission.
Marketo's Retry Algorithm
Instead of thinking about "soft bounces," it's more accurate to understand how Marketo, like most SMTP senders, handles email delivery failures using an exponential backoff algorithm. Here’s a breakdown of how this works:
Initial Retry Attempts: When an email fails to deliver, the first retry is scheduled for 5 minutes after the initial attempt.
Subsequent Retries: If the email continues to fail, the second retry happens 10 minutes later, the third after 20 minutes, and so on. This pattern continues with the interval between retries doubling each time.
Expiration Timeline: The email remains in the queue for up to 24-36 hours. The exact duration can depend on the specific Internet Service Provider (ISP) behaviors. For some ISPs known to be particularly problematic, Marketo may extend the retry period up to 36 hours.
Practical Implications of the Retry Process
While this algorithm ensures multiple attempts to deliver the email, it's important to note the following implications:
Delayed Failure Notifications: As the retries extend over hours, you won't receive a notification of failure until the email has fully expired from the queue. This means an email might attempt delivery for up to 36 hours before you are informed of its failure.
Immediate Failures: An email that expires in 24 hours likely encountered issues from the very start. This immediate failure indicates a persistent problem preventing delivery right from the initial send attempt.
Special Considerations
An essential aspect to consider is how the exponential backoff algorithm interacts with server stability. If a recipient's server was completely down when the email was first sent, and later it becomes partially available but remains unstable, the delivery chances decrease over time. The fewer opportunities the email has for delivery, the lower the likelihood it will ultimately be received.
Conclusion
Understanding Marketo's email retry algorithm helps clarify the misnomer of "soft bounces" and provides insight into the technical processes behind email delivery. Remember, the key to effective email marketing lies not just in crafting compelling messages but also in understanding the mechanisms that ensure those messages reach their intended audience.
Happy Marketo’ing! 💜