Fail or Pass: Understanding email bounces and deferrals

Fail or Pass

By Julia, Deliverability Expert

A saga of bounces and deferrals

As many of you are aware, we track the amount of fails each email encounters while it is attempting to send to your list of recipients. And, as some of you can attest, this can lead to some rather overwhelming statistics.

Before we get ourselves too worked up over a few failed email sends, let’s get a better idea of what we’re dealing with.

Our system, like many others of a similar nature, recognizes 2 types of failures:

Let’s think of soft fails as ‘deferrals’ – an email can defer multiple times & still ultimately go through. These can signify an impending block or simply be how that server delivers emails with a high volume of recipients.

Some servers, such as Verizon & Comcast, slowly deliver their messages so it can actually be common for them to have thousands of soft fails without having any hard fails. In some cases, a few messages may “time out.” This is still not necessarily a hard block.

Think of it as a waiting room with hundreds of people – they are either going to wait their turn (send) or they are going to get impatient and leave (time out).

Let’s think of hard fails as ‘bounces’ – an email can only bounce once. It either signifies a bad/invalid email, a server block, or the final soft fail.

It is important to look into these errors especially. Invalid emails should ALWAYS be removed from a recipient list; Server blocks always need appropriate attention and, when necessary, mitigation; and too many soft fails that permanently bounce means that we may be sending at too high of a volume.

Oftentimes, soft fails can be used proactively while hard fails generally require us to work reactively & learning how to best respond to both is key to successful email marketing. It is crucial to have an understanding of these types of errors because the quicker we respond to factors affecting our deliverability, the less damage they are able to cause.

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