Bouncing: Don’t Limit Success to Delivery

When it comes to delivering messages to the inbox, senders are always aiming for 100%. Unfortunately, the nature of email itself makes a 100% delivery rate nearly impossible—something the Deliverability Operations team often reiterates when we discuss healthy thresholds with our senders.

There are many reasons why messages will bounce back rather than successfully deliver. Hard bounces indicate an invalid address, or an address that no longer exists, but soft bounces cover a much wider range of issues—not all of which are always the sender’s fault.

So if some amount of bouncing or undelivered mail is a guarantee, how much is too much, and what is considered business as usual? Here are some thresholds to keep top of mind:

Hard Bounces Should Not Exceed 2%

A hard bounce will only be returned when a sender attempts to deliver to an address that is invalid or no longer exists. As such, hard bounce rate is a key metric to gain insight into the health of a list and assess whether it is active and up-to-date. In general, hard bounce rates should never account for more than 2% of a sender’s overall bounce rate. Even at a low threshold, crossing this volume will lead to reputation issues in the eyes of ISPs.

Overall Bounces Should Not Exceed 5%

Overall bounces rate includes both hard and soft bounces. Anything from a temporary hosting issue on the ISP’s side, to a recipient with a full inbox who is unable to accept mail, can be returned as a soft bounce. These temporary issues are expected from time to time, however, exceeding the recommended threshold could indicate a block or reputation issue is at play.

Although addresses will bounce from time to time for reasons outside of your control, this should not be taken as a get out of jail free card, or as an excuse to justify significant bouncing in your reporting. Keep in mind that any bounce rate that crosses the thresholds set above can trigger reputation issues at ISPs. As all senders know, this will only lead to exponential delivery issues if not addressed.

But it’s also important to consider the limitations of basing deliverability health on “delivered” rates exclusively. A message may be successfully delivered to an ISP, but sent to the spam folder rather than the inbox. Would you consider that a benchmark for deliverability success if no distinction is made?

When it comes to deliverability, consider the big picture. Don’t limit your outlook to messages delivered. Dig deeper and always take into account the engagement of your users with those delivered messages—including negative engagement metrics like spam complaints when available. But if you have to focus on delivery, know that some bouncing will always be outside of your control.

To be a mobile marketing rockstar, you have to give your customers a seamless experience. Considering that 40% of emails are opened on mobile devices, our Mobile Email Guide is here to help improve the mobile marketing experience.