What's the Difference Between a Hard Bounce and a Soft Bounce?

Do you occasionally pop into your email marketing reports, click around and become overwhelmed? We've been there! There are so many email marketing metrics, and if you aren't familiar with the different email metrics, then it's almost impossible to draw actionable insights from the data. So let's talk about an email metric that's important to email list hygiene and email deliverability: bounce rate. 

Email bounce rate measures the percentage of emails that you've attempted to send that have "bounced". An email "bounces" when an email is rejected by your email recipient's server. Each internet service provider uses the same basic principles but unique tests and criteria to determine whether or not an email should reach an email server. ISPs use this as another method to protect the inbox from spam.

According to Constant Contact, the average bounce rate for all industries is 9.94%. Hubspot recommends that your team should aim for a total bounce rate that is less than 2%. 

There are two types of email bounces: hard bounces and soft bounces. Understanding the difference between the types of bounces is important because it helps you decide what action to take. 

Hard Bounce vs Soft Bounce

When an email bounces, it returns a Simple Mail Transfer Protocol (SMTP) reply. The SMTP reply includes a bounce code that corresponds with a description of the issue. Your email marketing tool captures and stores this reply. Quality tools will also attempt to read the SMTP reply and categorize it as soft or hard, but the reply doesn't always contain the true reason for bouncing. 

Here are a few example codes and their descriptions:

• 4.2.2 - (soft bounce) email account is over quota
• 5.0.0 - (hard bounce) 
• 5.4.4 - (soft bounce) unable to route
• 5.6.1 - (hard bounce) media not supported

You can view a full list of bounce codes here. 

What is a Hard Bounce?

A hard bounce is the more serious of the two types of bounces. A hard bounce is a permanent delivery failure for a particular email address. You should immediately stop sending marketing emails to an email address that hard bounced. Hard bounces are linked to the email address, not the email subscriber record. For this reason, we do NOT recommend immediately deleting any hard bounces. We recommend reviewing the record for entry mistakes or other issues. 

Some email service tools will automatically clean email addresses that hard bounce from your email list. For example, ActiveCampaign marks hard bounces as “bounced” and automatically prevents the user from sending more messages to that email address. It's important to be familiar with how your ESP handles bounces and the associated contact records. 

A hard bounce occurs when an email address:

• has been entered incorrectly (knowingly or unknowingly) by the email subscriber
• was entered incorrectly by a member of your team

• no longer exists (deactivated account)
• is completely blocked by the recipient server

According to Mailchimp, the average hard bounce rate is 0.40%. If your organization's hard bounce rate is significantly greater than 0.40%, you should review how subscriber data is captured and entered. If your staff manually collects and enters email addresses, you might want to invest in a solution to automate this process. If subscribers are responsible for leaving their web address on a form, you might want to verify these emails before they are added to an email marketing campaign.  

What is a Soft Bounce?

A soft bounce is a temporary delivery failure for a specific email address. When you receive a notification of a temporary bounce, it's likely that the message can be successfully delivered to that email address in the future. 

It's important to understand how email service providers handle a message that soft bounces. 

It's equally important to understand how your email marketing tool handles soft bounces. For example, ActiveCampaign effectively treats a soft bounce as a hard bounce after an email address soft bounces 3 times in a row (3 separate campaigns). After these 3 soft bounces, ActiveCampaign marks the email address as bounced and automatically prevents the user from sending more messages to that email address.

Here are a few of the main reasons a soft bounce can occur:

• You have a high spam complaint rate. 
• Your domain/IP address has been blacklisted. 
• Your email message doesn't meet the recipient servers DMARC, anti-spam, anti-virus, and/or sender requirements. 
• Your email message is too large. 
• You have sent too high a volume of emails to the recipient server. 
• The recipient’s mailbox is full.
• The recipient's email account has been temporarily suspended.
• There is a problem connecting with the recipient server. 

According to Mailchimp, the average soft bounce rate is 0.58%. You want to closely monitor your soft bounce rate, but you also need to practice some patience while this issue is resolved. If you handle removing these bad email addresses manually, you will want to keep track of which emails have received multiple soft bounces. Once an email address reaches three soft bounces, you should remove this email address from your list to prevent further damage to your sender reputation.

As we mentioned above, ActiveCampaign automates this process. We highly recommend using ActiveCampaign or another email marketing tool that has this functionality. Some solutions allow for 7-15 soft bounces, depending on previous subscriber activity before converting the email address to a hard bounce. 

Wrap Up

It's critical for email marketers to understand and monitor metrics related to email deliverability. Email bounce rate is one of the simplest metrics to monitor and improve, especially if it's automated. If you use an automated system, we still recommend familiarizing yourself with what's going on behind the scenes. Contact your ISP and marketing email tool to make sure you understand how your email is interacting with their systems. If your email marketing tool is lenient with soft bounce, you might want to manually remove them sooner or switch tools. 

If you see a high percentage of bounces when sending email marketing campaigns, we recommend examining the methods with which you gather email addresses. Purchased lists are notoriously high in invalid email addresses (the list might also include spam traps). Please do not attempt to build your business using this tactic. Lead collection at events is another tactic that can lead to bounces. If your team manually enters the information, invest in a system to have leads enter this information electronically on site. Do you collect email addresses via online forms? We have all put in a random email address to avoid an email list. To prevent this practice from hurting your email marketing, use a verification check before it enters your email system. 

Paying attention to bounce rates is an easy way to boost your email deliverability rate and keep your list clean. Don't lose out on this easy email marketing win because you don't know the difference between soft and hard bounces.