Email Soft Bounce: Re-Attempted Delivery Protocol

[Matt_Underwood]

I recently created an email bounce management program and I want to make sure the soft bounce emails are being categorized the right way. In order to set the program up, I need to know what the Marketo soft bounce email re-attempted delivery protocol is.

Essentially, I want to know how many times a soft bounced email attempts redelivery, and over what time frame this occurs. 

I've seen a few different answers for this question, but have been unable to find anything in the official Marketo Docs.

Any help is much appreciated! Thanks in advance.

[Devraj_Grewal]

Matt,

I have actually simplified our smart campaign for soft bounce management. Once they soft bounce 3 times, they are considered email invalid. I probably wouldn't spend too much time investigating each soft bounce issue.

[Matt_Underwood]

This is how I currently have the program setup but I was concerned with two potential edge cases (listed in response to Sanford's comment below). 

[SanfordWhiteman · Accepted solution]

Let's not use the term "soft bounce": it doesn't conform to actual SMTP reality, which appears to be what you're asking about.

If you mean "what is the MX retry algorithm" Marketo (like most SMTP senders) uses an exponential backoff algorithm. The first retry is in 5 minutes, the second is in 10 minutes, third is 20 minutes, etc. The message expires from the queue after 24-36 hours (36 is for certain known-ill-behaved ISPs).

Why do you care about this level exactly?

[Matt_Underwood]

This is very insightful and I wasn't aware of the terms you used prior to this conversation (SMTP and MX retry algorithm). 

I wanted to make sure the bounce management program I created had the correct "date of activity" for the soft bounce lists and wasn't too narrow of a time frame (causing a soft bounce to be recorded while it was still undergoing redelivery attempts). I was also concerned that a single soft email bounce could be recorded multiple times during the attempted redelivery window. 

Now that I've done more research on the terms you provided, I don't think this will be an issue. 

[SanfordWhiteman]

Yes, an email may not conclusively soft bounce (I really hate the term, sorry) expire from the outbound queue until delivery has been attempted for 36 hours, with ever-lengthening retry intervals in that time.

On the other hand, while you won't get notification that delivery attempts were failing until it finally expires, you may want to point out -- depending on who you're communicating with and how much detail they ask for -- that an email that expires in 24 hours must have been failing from the very start, by definition.

A final element to bear in mind is that the backoff algorithm means if a recipient's server was down completely when you first sent the email, then later came up partially but was unstable (repeatedly going up and down) the email may or may not be delivered, since it gets fewer and fewer chances as the day goes on.