Email Bounce Rates: Hard Bounces vs Soft Bounces


There are all sorts of reasons why an email might fail to be delivered and bounce back to the sender. Most of these reasons lie outside of your control as an email marketer, as you’ll see in a moment. But what you can control is how you respond. 

Keeping your bounce rate as low as possible, especially your hard bounces, plays a big role in maintaining a strong email reputation. That helps you achieve consistently high deliverability, and that means better results.

If you don’t attend to your email bounces, and just keep sending messages to non-existent email addresses, you increase your chances of being flagged as a spammer and getting blocklisted. And that will keep many of your actual, interested subscribers from receiving your emails, too. 

So, keeping control over your bounces is a big part of managing a successful email marketing program.

Bounce rates: web vs email metrics

First, let’s clarify what we mean by a bounce rate. There may be some confusion here because website traffic data also includes a metric called a “bounce rate.” But the bounce rates you see in Google Analytics have very little in common with email bounce rates. 

A website bounce rate measures how many visitors come to your site, look at one page, and then leave without taking any actions or visiting any other pages. A high web bounce rate usually means your content isn’t very engaging, your site is loading slowly or giving off red flags like security warnings, you’re attracting the wrong audience, or you’re just giving visitors little reason to browse further. 

An email bounce rate measures how many emails do not get delivered compared to how many emails you send. If you send 5000 emails to your list, and 50 of them bounce back and don’t get delivered, you would have a fairly acceptable bounce rate of 1%. A high email bounce rate is a sign that you need to conduct some list cleaning.

What is a high email bounce rate?

If your email bounce rate is too high, a mailbox service provider (MBP) can penalize your sender reputation. They take it as an indication that you’re not maintaining good list health or are acquiring subscribers from less-than-legitimate sources. 

For this reason, the general recommendation is to keep your bounce rate under 2%, if possible. Once you creep above the 2% bounce rate benchmark, you need to perform some email list cleaning and get your bounce rate back down. 

Why not go for a zero bounce rate? Well, that’s certainly the goal, but it’s not exactly realistic. Bounced emails will happen eventually. People abandon addresses because they change jobs or enter a new phase of life. Some bounces are temporary issues and have nothing to do with maintaining a clean contact list. Even a full mailbox could cause bounces. ISPs understand this and there’s a bit of grace.

However, some email addresses will keep bouncing no matter what – like a bouncy ball with enough energy to keep bouncing for all eternity. (Sorry for the dramatics.) So, how do you know which type of email bounces to worry about the most? It comes down to hard bounces vs soft bounces.

email bounce

What are soft bounces?

A soft bounce happens because of a temporary situation with the recipient. This sort of bounce won’t typically result in immediate penalties, and it will cease once the issue is resolved. 

Causes of soft bounces include:

Mailbox full

Most mailbox providers give quite a large amount of room for each account. A full mailbox suggests that the recipient has stopped using that email address. It could also mean they just don’t delete old emails frequently enough, or that they have a lot of images or rich media in emails taking up space on the server.

Size of email

Some mailbox providers place limits on the size of emails they’ll accept, in terms of megabytes. So if you’re sending out emails with lots of high resolution images or huge attachments, you run the risk of them not being delivered. The simplest way to avoid this is to always optimize your images. 

You can also test for inbox placement and email deliverability before sending a major campaign. 

Receiving email server issues

Here, the recipient’s email server might be down or be having other issues preventing it from receiving messages at that time. After a while, it will work again and the email will go through.

A recipient’s mail server may also bounce a message  back to the sender if it fails email authentication protocols like SPF, DKIM, and DMARC enforcement

What are hard bounces?

A hard bounce indicates a much more permanent problem compared to a soft bounce. With a hard bounce, the email address is undeliverable and isn’t likely to become deliverable in the future. You want to remove hard bounces consistently because these are the ones that do real harm to your email reputation and deliverability, ultimately impacting your results.

Some ESPs will just remove hard bounces for you because they too want to keep their own reputation as a sender as pristine as possible, and hard bounces don’t do anyone any good.

Causes of hard bounces include:

Non-existent email address

How can an email show up on your list if it doesn’t exist? It may have been real before, but perhaps that recipient closed their email account. If it was a work email, they may have left their job. Eventually, abandoned addresses may be used as spam traps

So, if you keep sending to non-existent email addresses, you’ll not only have a higher bounce rate, but you may accidentally send to a spam trap and end up on a blocklist. 

Another cause of non-existent emails is typos. A real person may have opted into your email list but just typed their address wrong. If this happens, sometimes you can correct it. For example, if you notice their email address ends with, you could can manually add the missing ‘m.’ The same goes for other common typos. But if they mistype the personalized portion of their address, catching a typo will be much harder.

example of a typo spam trap

Of course, manually fixing little subscriber typos is finicky, and even a bit risky. You can’t be 100% sure that person truly meant to give you consent to send them email marketing campaigns. That’s why a solution like InboxReady’s Email Verification API can help. It catches common typos and provides potential subscribers with suggest fixes.

You’ve been blocked

Some mailbox service providers block emails perceived to be commercial in nature. Again, this is most likely with certain companies or institutions, such as government entities. You may be able to get around that by contacting these subscribers through other means and asking them to add your sending email address to a “safe senders” list. 

In other cases, recipients themselves can block you, perhaps because they don’t want to receive emails from you but also don’t want to go through the unsubscribe process for some reason. If you continue seeing this as the reason for an email bounce, it’s best to just remove that subscriber from your list.

Why do email bounce rates matter?

As we already mentioned, an unattended email list will eventually turn against you. It’s only a matter of time. People will close or abandon accounts, move jobs, give fake or mistyped email addresses, and do other things to make their email addresses undeliverable. 

If you don’t attend to it, your bounce rate will continue to climb. It’s inevitable. Too many bounces make you look spammy.

And if you surpass the average email bounce rate of 2% and do nothing about it, some MBPs will eventually start to block you or send your email messages to spam folders. You could end up on a blocklist, which means more MBPs may start to turn you down. It snowballs. 

If you don’t maintain a low bounce rate, you will damage your sender reputation and your deliverability will suffer. You may not even be able to get through to your best subscribers who are eager to hear from you.

A high bounce rate may also prompt your email service provider (ESP) to suspend your account. For example, Mailgun by Sinch has an Acceptable Use Policy that asks senders on its platform to keep their bounce rate to 5% or less. That’s because when senders are using a shared IP, a bad reputation can impact deliverability for other senders.

You want to remove hard bounces consistently because these are the ones that do real harm to your email reputation and deliverability, ultimately impacting your results.

Bounced emails and your other metrics

Can a high bounce rate have a negative impact on other email metrics? Well, it is most certainly a bad sign for your email deliverability, so you’ll see the delivery rate go down as bounces rise.

However, bounced emails should not affect open rates or click-through rates. The email open rate excludes bounces before it is calculated. In terms of measuring deliverability, email bounces won’t impact your inbox placement rate either. Thats because inbox placement only measure messages that are delivered to the recipient’s inbox.

How to reduce your email bounce rate: Four best practices

There are a number of ways to reduce your email bounce rate, but it all comes down to not sending emails to non-existent or problematic email addresses. Remove them from your contact list, and they stop bouncing. But how do you keep up with this?

Here are four ways:

1. Use a suppression list

With a suppression list, any email address with a hard bounce gets added to a list, and even if you don’t unsubscribe that person, you won’t be able to send any future emails to them as long as they remain on this list. 

The biggest advantage of this approach to reducing bounce rates is that it’s automated. You can set it up so hard bounces automatically get added to a suppression list. That way, you don’t have to go in every time you send an email and manage all the bounces. In fact, your ESP may already suppress hard bounces for you. Mailjet by Sinch, for example, automatically removes these types of contacts from your list. Check with your service provider to find out for sure.

2. Perform list hygiene

Clean your email lists regularly by removing undeliverable addresses. This sounds good in theory. But it’s more efficient and an even better idea to keep them from ever getting added to your list in the first place.

With email verification from InboxReady by Sinch, you can verify that every new subscriber is a real, actual person with a valid email address when they signup. That’s thanks to the real-time verification API. This keeps disposable email addresses, typos, and other problems with new opt-ins from sneaking onto your email list and hurting your deliverability. 

Email verification also does this with your existing subscribers when you need to validate contacts in bulk. This matters just as much as new opt-ins because, as mentioned earlier, some formerly good email addresses go bad when people move, close accounts, or make other changes in their lives. 

3. Use a double opt-in

While there are some marketers who shy away from the double opt-in process, because it adds an additional step that could affect email list growth, it truly is a good best practice to follow.

When a new contact fills out an online form, you send a follow-up email message asking them to click a link and confirm their desire to subscribe. If it’s an invalid email address that would create a hard bounce, they won’t get the message and the contact stays off your list.

Yes, there will be some people who miss the confirmation email. Chances are, however, they were unlikely to be a very engaged subscriber anyway. The double opt in is also a good way to reduce spam complaints and stay in compliance with data privacy laws. That’s because the process provides proof that contacts gave you consent to email them.

4. Watch your deliverability metrics

inbox placement report with email bounce rate

If your sending email address or IP did get added to a blocklist – even by mistake – would you know it? 

Monitoring your deliverability plays a key role in keeping your bounce rates low, because if your deliverability starts to suffer, that means something isn’t right. You might have a spam trap that found its way to your subscriber list. You might have been placed on a blocklist. 

And if that happens, the deliverability monitoring features from InboxReady by Sinch will help you chart a course of action. Plus, Inbox Placement reports provide you with data about your email bounce rate so you can track it and watch it improve over time.

See the full suite of email deliverability tools from InboxReady to help you get delivered. 

Author: The Email on Acid Team

The Email on Acid content team is made up of digital marketers, content creators, and straight-up email geeks.

Connect with us on LinkedIn, follow us on Facebook, and tweet at @EmailonAcid on Twitter for more sweet stuff and great convos on email marketing.

Author: The Email on Acid Team

The Email on Acid content team is made up of digital marketers, content creators, and straight-up email geeks.

Connect with us on LinkedIn, follow us on Facebook, and tweet at @EmailonAcid on Twitter for more sweet stuff and great convos on email marketing.

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