What is a Email Bounce? [Three Ways to Lower Your Bounce Rate]

Regardless of whether you’re sending marketing or transactional email, one thing that every email sender wants is good deliverability.  Email senders invest a lot of time, effort, and money to make sure their emails are landing in the recipients inbox. So how can you optimize your deliverability?  Frankly, there is a lot that goes into it, but one huge factor is managing your email bounces. We are going to dive deeper in to what is a bounced email and how bounce rates affect your email deliverability.

Table of Contents:

• What is an email bounce?
• Why do emails bounce back?
• How to fix bounced emails?
• Types of email bounces
• What is email bounce rate?
• 3 Ways to lower your bounce rates

What is an email bounce?

A bounce is when a sent email makes it to the recipient server but encounters an error before making it to its final destination.  A common misconception is that all email failures are bounces which is simply false.  There are two types of email failures, asynchronous and synchronous.  A bounce is an asynchronous failure, meaning the email makes it to the recipient server and fails sometime after that.   A bounce is NOT a synchronous failure which is a failure that happens earlier, in the the server communication process. This means that in order for an email failure to be considered a bounce, the failure must occur after making it to the recipient server (asynchronous).

Why do emails bounce back?

Email messages will bounce due to inaccessibility en route to the recipient’s email server. There’s a variety of reasons an email will bounce back, including:

• Full inboxes
• Unresponsive servers
• Email Addresses that no longer exists
• Invalid email addresses
• Fake email addresses
• Email Address Typos
• Blocklisted / Blacklist emails

How to fix bounced emails?

Fixing email bounces depends on the type of email bounce. A hard bounce is permanent, but all isn’t lost, hard bounce emails can still be add the offending email addresses to a suppression list, which will help bring down the bounce rate. A soft bounce is normally something that can be remedied fairly easily depending on what exactly is going on.

Types of email bounces

While the overarching concept of an email bounce is relatively simple, there are some underlying topics that also must be considered to fully understand what email bounces are and how they affect your deliverability.

There are two primary types of bounces in email, hard and soft.

What is a hard bounce?

A hard bounce email is an email that has been permanently rejected due to something that has occurred after making it to the recipient server.  This will typically happen when the recipient email address is invalid. For example, maybe the domain name does not exist, the email is no longer active, or the recipient is simply unknown.

What is a soft bounce?

The second type of email bounce is a soft bounce email which is a temporarily rejected email.  Similar to a hard bounce, a soft bounce also makes it to the recipient server and is rejected shortly thereafter.  A soft bounce is unlike a hard bounce because it is not a permanent failure and could still be delivered successfully at a later time.  A soft bounce might happen when a recipient’s mailbox is full and unable to accept more mail, or the email is too large to process.

As an email sender, it is your responsibility to make sure your email bounce rates stay as low as possible – your deliverability depends on it!

Hard bounce vs Soft bounce

Hard bounce emails are refused emails that will not be looked at again due to an error occurring once arriving to the recipient mail server, these are permanent reasons. Soft bounce emails are just like hard bounce emails as in they get to the recipients email server and run into an issue and is rejected, however soft bounce emails aren’t permanently rejected, for reasons that are more dynamic like a full inbox, too large of file size, or another reason where the outcome can be adjusted to allow the email to pass through successfully.

What is email bounce rate?

The percentage of emails that are unable to be delivered to recipients is called the email bounce rate. Not to be confused with email open rates or click through rates.

Typically, bounce rates will be a larger topic of concern for email marketers compared to transactional email senders.  This is because marketing email is typically perceived as being less important to a recipient and may not perform as well.  Email marketing lists can be old, less reliable and naturally will cause more bounces. Because of this, email marketers have to remain on top of their bounce rates to maintain good deliverability. Unlike marketing email, transactional email is usually a warranted email response triggered by a user’s action on an application or website like an order confirmation or email receipt. This means that the email was  most likely sent to a legitimate, active email address which will be less likely to bounce. With that being said however, if a transactional email sender notices high bounce rates, it could be the sign of a major underlying problem within their email infrastructure that demands immediate attention.

What is an acceptable bounce rate for emails?

An acceptable bounce rate is anything close to .1%, however the average is 2%. Email bounces are going to be unavoidable in small numbers, so measuring by a percentage can help better keep an eye on the amount of bounces occurring, so that if a industry standard benchmark of 2% is reached or surpassed, further investigation can take place to remedy before further damage is done.

What is a high bounce rate?

The number of emails that bounce compared to the total number of emails you send is a percentage referred to as the bounce rate. For example, if you send 50,000 emails and 5,000 of them bounce, your bounce rate would be 10% – Yikes! Time to speak to a professional. A high email bounce rate is anything over 5%. Normally any email bounce rate of 5% or even as high as 10% is cause for alarm as it suggests a serious issue requires attention immediately.

3 Ways to lower your bounce rates

To optimize your email deliverability, an acceptable email bounce rate will be anything less than .1%, but this number will vary depending on your unique situation.  If your bounce rate starts to increase, mailbox providers will take note of your email traveling back through servers and could mark your email as spam. Once this happens, inbox placement will suffer, with more of your mail going straight to recipient’s spam folders.

So what can you do as a sender to keep your bounce rates as low as possible? Here are a few tips on how to lower your email bounce rate:

Regularly clean your email lists

Recipients who complain, bounce, or have not interacted with your email in a while should be regularly cleaned from your sending lists.  This will not only reduce your risk of bounces, it will also reduce the amount of negative engagement your email receives. This type of “list hygiene” can go a long way in improving your overall email deliverability.

Send email only to opt-in lists

Sending your email only to people who want to receive them will decrease your bounce rates and increase your engagement.  We highly advise against sending your email to a purchased email list as it will severely damage your sender reputation and overall deliverability.  To learn more, read our blog on the risks of sending to a purchased email list.

Immediately remove hard bounces

It is important that you remove hard bounces from your email lists immediately after the bounce occurs.  Hard bounces are monitored by mailbox providers very closely and will greatly impact your deliverability if not taken care of.  Being that this task can get incredibly tedious, many senders will use an email service provider like SocketLabs who has built in bounce processing that will automatically add hard bounces to a suppression list so these inactive addresses do not continuously receive your email.

Again, email bounces are just one small piece of  the greater email deliverability puzzle. While you should always be looking to get your bounce rates as low as possible you should also be focusing on the greater topic of deliverability. Deliverability can be a large topic to handle on your own.  Many high volume email senders will use email service providers, like SocketLabs, to help build their email infrastructure and maximize their deliverability. If you want to learn more about how SocketLabs can help build and optimize your email delivery solution for free, visit our pricing plans page.