Understanding Bounce Codes

The Importance of Data Quality

Written by Monica Marino

Written by Monica Marino

Last updated on Dec 11th, 2019

Why Care About Bounce Codes?

Prospecting takes time, and time is money. This guide it’s essential for you to understand why your emails aren’t making it to your prospects’ inbox. 

Let’s begin by defining what is a bounced email.

Simply put, a bounce message is an automated reply from the prospect’s email server notifying you that the email was not delivered. 

In outbound sales, delivery correlates directly with replies. Replies correlate with conversions. And with conversions directly linking to pipeline and hitting quota, you could say that it’s kind of a big deal to lower bounce rates. If you need more of a reason to worry about it, consider that bounced emails negatively affect your IP reputation. This correlates to how emails get blocked, flagged, or blacklisted.

Let’s talk about what you can do to monitor your email address.

Check your spam score. This is a numerical rating (0-10) that takes several elements into account. There are two primary ways emails can get blocked. The first is automatic email filters and the second is an email being manually marked by the recipient as spam. Both affects your spam score. So a good place to start is to use free sites available like to understand if your emails are at risk.

Understanding Two Types of Bounces

Soft bounces versus hard bounces are the two categories of bounce messages. A soft bounce (which starts with a “4xx”) which in most cases can be fixed doesn’t affect your spam score as much as a hard bounce. This is why it’s important for outbound sales reps to use reputable data sources to maximize deliverability. In today’s day and age, employees change jobs more frequently, which means an increase in data degradation that currently averages to 24-36%. That means that ¼ of your email will hard bounce due to bad data.

So What are the Differences?

A soft bounce is a temporary issue related to the prospect’s server. The email address may be unavailable or full. The prospect’s server could have insufficient storage or issues processing the delivery. The good thing with soft bounces is that they will eventually be fixed. But be patient because five consecutive undeliverable attempts will turn to a hard bounce.

On the flip side, a hard bounce (starting a with a “5xx”) will never turn into a soft bounce. These errors are permanent and cannot be fixed.

Nevertheless, some email deliverability errors are in your control and others are not. So let’s dig into common reasons why emails bounce that are in your control.

Good & Clean Data

  • Data degradation is at an all time high, so don’t use unreliable contact lists. Buying lead lists is dead. Successful sales teams use sales automation tools that provide verified email addresses. In most cases this is done by using a browser extension that computes the email addresses using an internally built algorithm. 
  • Scrub your list to remove incorrect or old emails which affect bounce rate and your spam score. Sales automation tools can provide the validity of the email addresses so you can remove all invalid emails.

Segmentation & Personalization

  • Understand your company’s buying personas and the target market. This can prevent your emails from being manually marked as spam if the emails are being sent to the wrong audience.
  • Test catchy, unique, short and sweet subject lines. Also try A/B testing messaging. If you aren’t, you are losing the opportunity to understand what works and what doesn’t to increase open rates and reply rates.
  • Ask yourself if the prospect’s pain points are addressed clearly and concisely. If they are not, edit the message because the goal of personalization is to have the data points resonate. Sales enablement tools like FoxBound can make this process seamless. And the more unique the message, the less likely your email will be sent to spam.

Spam Filters Triggered by your Email Content:

  • Keep the exclamation points to a minimum. This is one example of many triggers that Google and Outlook are looking for to block emails that are likely to be spam.
  • Use standard formats and fonts. This includes capital letters and crazy colors if you want your email to reach the prospect
  • Compress images and check your image to text ratio. Spam filters look for large embedding image. It is also recommended that an email should consist of about 70% text and 30% images to avoid filters.
  • Remove excessive links. Emails will be flagged and sent to spam if the text contains more than six links.
  • Review the text to avoid common spam words that are blocked in subject lines and in the body of an email.

What is an Acceptable Bounce Rate?

There are some factors out of your control. Even if you do everything in your power to follow the guidelines above to ensure emails are received and your messaging resonates with your audience. That said, note that an acceptable bounce rate is between 2-5%. Anything over 5% suggests a significant problem that you will want to resolve.

Formats of Bounce Codes

It’s important to understand bounce codes to solve delivery problems. The traditional SMTP bounce reasons are three-digit codes (550), and the enhanced SMTP bounce responses are three-digits separated by decimal points (5.1.1).

 Full Bounce Code List Here 


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