I’m sure you’ve been in this situation before. You type up a nice, detailed email as a reply to your doctor, the government etc. but when you click send an error message flashes up – “Your message could not be sent”. That’s an example of an email bounce back, and today we’ll be taking a look into why they’re important to keep an eye on.

What Is An Email Bounce?

An email bounce is any time one of your sent messages fails to reach the inbox of the intended recipient. This can happen for several reasons, but the most common ones are addresses not accepting replies, your address being blocked by that particular domain or address, and the account simply not existing to receive the mail in the first place. Whichever one is the case, a bounce is a bounce and will hurt your chances of succeeding in the marketing world.

Why Should I Care About Bounces?

If we lived in a world where everyone got along things would be much better. Unfortunately we don’t, and there are plenty of reasons for internet service providers (ISPs) to be suspicious of anyone with a high bounce rate.

If you’re getting plenty of emails bouncing, it means you’re not checking your email lists to see if they’re valid or not. It’s also one of the main indicators that someone might be trying to distribute spam or malware, since malicious, bot-driven emails are often sent to all possible usernames in a particular domain, regardless of whether or not they’re real.

Because of this, having lots of bounces will mean the ISPs will flag you as suspicious and potentially mark your messages as spam or potentially harmful, which is the last thing you need when you’re sending out marketing emails.

How Do I Check My Bounce Rate?

A bounce rate is the proportion of your emails that are being “returned to sender”, usually expressed as a percentage. If you have email campaign management software this number will usually be automatically available to see on the dashboard, if not you can calculate it by dividing the number of emails that bounced back by the total number sent.

A high email bounce rate is usually considered to be anything above 2%, depending on your industry. Essentially, you can only have twenty out of every thousand emails you send bounce back before it hurts your reputation as a sender.

For industries with high email address turnovers, for instance anything aimed at college students who usually only have their email address for a few years, a higher rate is more acceptable. Not every ISP will take this into account however, so you need to be on the ball and remove as many inactive email addresses from your subscriber lists as you can.

Hard And Soft Bounces: What’s The Difference?

There’s two types of email bounce, referred to as hard and soft bounces. If you imagine a postman delivering physical mail, a hard bounce would be a letter with the wrong address written on it whereas a soft bounce would be an address where the mailbox is full and can’t fit any more letters in.

In the case of soft bounces, plenty of ISPs have rules that let you retry sending the mail a few times before it’s considered a hard bounce, similar to the postman trying to deliver your letter multiple times before deciding the box isn’t ever going to be emptied. Some reasons for a soft email bounce include:

• The destination mailbox being full, as with the example above.
• The email servers being temporarily down, as if the postbox has been stuck shut.
• The email contains unsupported files or files that are too large, akin to a postman trying to fit a package through a letterbox that is clearly too small for it.
• The recipient has turned on “out of office mode”, as if there’s a sign on the letterbox saying “no post please, I’m not here right now”.

Since soft bounces can happen for several reasons, ISPs allowing multiple attempts is useful, but you should check with each individual one what their protocols are regarding these temporary setbacks.

Soft bounces can also happen if your reputation has aroused suspicion by the ISP, so you should try to find out more about what caused this if you can, lowering your email campaign volume while you do.

Hard bounces on the other hand, are a sign that the destination email address simply doesn’t exist. Whether it did at one point or simply was a ruse from the start, the way to go is to cut the address off your list completely. Hard bounces are a significantly stronger blow to your reputation than soft ones, so it’s best to cut the number as early as possible.