Bounce Parameters, Budgets, and Deliverability

Do you know the specifics of your bounce parameters and if, or when, e-mail addresses are removed from your list for bouncing?

At a basic level, there are two kinds of bounces: hard and soft. In general terms, hard bounces suggest terminal inability to deliver, while soft bounces may reflect a temporary delivery problem.

Now, I know it’s not quite that simple. There are many different flavors of hard and soft bounces, and many who know the details argue against the “black and white” that these terms suggest, in favor of shades of gray. But if your e-mail service provider (ESP) is automatically removing e-mails that bounce, which they should be, then parameters define when those suppressions happen.

Awhile back I worked with a client that had a very high rate of bounce backs on every send. When we investigated, we found that these bounce rates had been steadily growing over the course of more than a year.

Further investigation found the cause: no soft bounces were being removed from the list. The client sent to e-mail addresses that had steadily returned bounces for a year or more.

This situation is problematic in a couple ways. First, the client was paying its ESP on the send quantity — so they were spending money, month after month, to send to e-mail addresses that had been bouncing for an extended period of time. Not the best use of their budget.

In addition, continuing to send to e-mail addresses that consistently return bounces can damage your e-mail reputation, which can in turn decrease your deliverability. Many spammers don’t clear bounces from their lists, so mimicking this behavior can make you look like a sender of junk mail to many ISPs.

When we contacted the ESP, they stated that soft bounces were automatically removed from their customers’ lists. Most ESPs will remove hard bounces after they occur once and soft bounces after they’re returned for three to five consecutive sends. This ESP initially didn’t believe, and later couldn’t imagine why, the automated process didn’t seem to be working for this client.

But then we figured it out. The customer was sending a single monthly e-mail to the list. The parameters around removing soft bounces required a soft bounce to be received on three consecutive sends within a 30-day period. That last part was the problem.

Because this client never sent three e-mails within a 30-day period, no one on the list ever registered more than one soft bounce in a single 30-day period. Therefore no e-mail addresses, not even serial bouncers, were ever removed for bouncing. We were able to refine the time frame, which solved the problem.

One ESP I recently worked with takes a different approach. It puts the onus on the client to define the bounce parameters at account set-up.

While this opens the line of discussion, many clients aren’t familiar enough with the concept of bounces to understand the issues. Education is required — enough to make a good decision, but not so much as to confuse the customer and send their minds spinning about the various types of hard and soft bounces (because most systems don’t allow you to set parameters for each individual flavor of each).

Bounces are a tricky issue. You don’t want to remove addresses that may be deliverable at a future date, but you also don’t want to keep serial bouncers on your list. There’s some margin of error here; it’s unlikely that any automated system will make the right decision on suppression 100 percent of the time.

Bottom line: ESPs have an obligation to understand the client’s send frequency, educate the client on bounces, and make reasonable recommendations on automated bounce parameters. If you’re using an in-house system, then the responsibility for setting reasonable bounce parameters rests squarely on your shoulders. Don’t just leave it to your IT group.

If you haven’t had this discussion with your ESP or IT group, or if you haven’t had it in a while, there’s no time like the present. Contact them and ask some questions. Find out what parameters drive suppression of bounces for you lists. Share your send frequencies with them and work together to see if the bounce parameters make sense for your e-mail program. If not, ask that they be adjusted.

Getting the balance right can be the difference between removing addresses that might be deliverable in the future — and spending money as well as jeopardizing your deliverability by sending to e-mail addresses that will never reach the recipient.

Until next time,


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