deliverability letter

Bounce Rates: Why They Can’t Be Ignored (And Why They’re Not Always Bad): A Blog About Hard Bounce and Soft Bounce Rates

Thoughts by Gracija Atanasovska • Writer Bento

Hard and soft bounces are terms you’re going to hear pretty often in email marketing. After all, email bounces are closely connected to email deliverability.

Email bounces are inevitable. As part of your email marketing campaign, you’re bound to experience email bounces (pun intended!). And even though they may seem pretty harmless, it doesn’t mean that they should be avoided. On the contrary - ignoring them may lead to high bounce rates, which in turn may lower your deliverability rates. And then it’s like a chain reaction that can negatively affect your whole marketing campaign.

So, in order to avoid all of this, let’s take a deeper look at email bounce rates and find out when you should look out for them as well as how to improve your email bounce rates in the long run.

What Are Email Bounce Rates?

Email bounce rates is a metric used in email marketing to determine how many of your emails have not been delivered to the intended addresses. When this happens, you’ll get an automatic notification that the delivery has failed. It means that the mail server of the recipient did not deliver the intended messages and the reasons for this failure can be multiple (I’ll talk about them in the sections below).

What are the Contents of an Email Bounce Message?

The bounce message that you receive when your email delivery has failed contains important info that can help you find out the reason why your email hasn’t been delivered. The info you’ll encounter in these messages will usually refer to:

  • The mail server that bounced the email;
  • The date and time when the message bounced;
  • The RFC (request for comments) code along with the reason why the email bounced. The RFC is a document authored by a range of computer scientists, engineers, and technicians (called the IETF). The RFC states that soft bounces should be described in the 4XX code, and hard bounces are described in the 5XX code. Take note, though, that not all internet providers (ISPs) will stick to these standards - you may encounter exceptions that’ll feature another type of code.

Soft Bounce vs. Hard Bounce Email - What’s the Difference?

When we talk about email bounces, we usually refer to either soft bounce or hard bounce. Let us explain both terms.

What is Soft Bounce Email?

A soft bounce email means that there has been some temporary issue that prevented the email from being delivered. The email recipient's address is valid and the email reached the mail server of the recipient, but something has prevented it from reaching the inbox, like full inbox, the recipient being offline, and so on.

What is Hard Bounce Email?

Hard bounce email occurs when the email you’ve sent to the intended address has been rejected permanently. This usually means that the addresses were invalid, that they’re fake, or don’t exist anymore, so the email had to be promptly removed.

Reasons Why Emails Bounce

Emails bounce for a variety of reasons and they’re not the same for soft and hard bounces.

Some of the common reasons for soft bounce emails can be:

  1. The mail server was down. Servers crash, overload, or they’re under maintenance - anything can happen, but it’s no big deal since it’s usually fixed in no time. Often, you’ll just need to resend the email.

  2. A full mailbox (the user doesn’t have any more free space in their inbox);

  3. The size of the email - the message was too big for the inbox of the recipient. This can happen if the email contained images that were too heavy or an attachment that exceeded the size limit.

  4. If the recipient set up autoreply - sometimes emails can bounce if the person on the other side set up the autoreply option and is temporarily not answering any emails.

The reasons for a hard bounce are different, so here are the most common ones:

  1. The recipient's email address is fake - it’s what people do, they sometimes give addresses that don’t exist to avoid receiving any emails, but still want to use some benefit of the signup process (a promotion, a discount, or a free item). A double opt-in is the magic cure for these kinds of situations.

  2. The recipient's email address is invalid or incorrect - this can be the result of unintentional typos when the user was filling in their address.

  3. Your email has been blocked - this usually happens with domains that have strict spam filter settings (government agencies and certain institutions that put a high priority on security). This can be solved by asking these organizations to add your address to their email list. And sometimes it can be the result of the recipient blocking your email address on purpose.

How to Improve Your Email Bounce Rate

As you were able to see, soft bounces are not that scary and they tend to resolve relatively quickly. Hard bounces, on the other hand, are more serious, and if you experience both hard and soft bounces regularly it can severely affect your email deliverability rate.

So, in order to prevent that, let’s take a look at the best ways you can maintain a low number of email bounces and improve your email deliverability.

Don’t Forget to Clean Your Email Lists

Maintaining email list hygiene is one of the most important ways to avoid email bounces, especially hard email bounces. Make sure to clean your lists at regular intervals (every 3 or 6 months) so that you don’t send to invalid or fake email addresses or people who haven’t responded in ages.

Use the Double Opt-in Option During Sign Ups

Luckily, nowadays it’s easy to control who gets on your email lists and more importantly - who actually wants to be there. The double opt-in process means that once the user fills out their address and data in the signup field, you send them a confirmation email, accompanied by a link they need to open to make sure that they really want to subscribe and be on your email list. It’s also a great way to check the validity of the email addresses used for signup.

Implement List Segmentation

List segmentation is the process of breaking up your list of contacts into different smaller target groups (also called segments). These lists will allow you to send more specific emails to different types of subscribers and communicate with the most engaged subscribers on your list. In turn, these emails will be interpreted by the spam filters of the ESPs (email servers) as emails with good content and even better engagement.

Send Emails at Regular Intervals

When you regularly send emails to your subscribers, it leads to higher engagement, fewer spam complaints, and lower bounce rates. Of course, this doesn’t mean that you should send too many emails. Just keep it consistent and send relevant information to your customers.

Make Sure to Authenticate Your Email

Email authentication allows you to strengthen your email reputation. You can authenticate your email by consistently using one or several addresses if you send from more than one. The key thing here is to make sure they’re always the same addresses - this is what I mean by consistency. Also, make sure to use SPF authentication which will stop spammers from sending emails from your domain. You can also use DMARC authentication which allows you better control of your domain and protects you from hackers. Using and properly configuring DKIM signatures makes it easier for you to be identified as a valid and secure sender.

And don’t forget to prepare for BIMI (Brand Indicators for Message Identification), the emerging new way of authenticating your emails by attaching your company’s logo to the message. It’s a straightforward, visual type of verification that makes it easier for your subscribers to trust where the emails come from.


Remember that you can’t completely do away with bounces. Your email marketing campaign will always experience a certain amount of email bounces. As you were able to see, people get their addresses wrong, servers crash or go under maintenance. This will keep happening, so what’s important is to keep the number consistently low by addressing your deliverability issues on time and by following good email practices.