Overview

What is a high email bounce rate?
Soft Bounce vs Hard Bounce
What causes emails to bounce back?
How to reduce your email bounce rate?

What is a high email bounce rate?

Before we talk about how to reduce your email bounce rate, we should set the baseline for what’s considered a high bounce rate. An email bounce rate is the percentage of your emails that bounce back as undeliverable. Email bounce rate is calculated by taking the number of email bounces divided by the number of delivered emails and multiplying by 100. For example, if you send 10,000 messages and you had 500 bounces, your bounce rate is 5% (50/10,000*100).

Unlike other email marketing metrics like clicks and opens, where a  high rate = positive, a high message bounce rate is negative. You want to keep your bounce rate as low as you can, roughly no more than 2-3%. Bounce backs (especially hard bounces) damage your reputation.

If your undeliverable email rate is high (above 5%), the negative deliverability will impact the success of your campaigns and email performance - future email campaigns included. That’s because email networks monitor bounce rate trends for all your current campaigns to decide if they’ll accept your emails later on.

Soft Bounce vs. Hard Bounce

Think of soft bounces as blocks that are a short-term issue – you don’t need to permanently unsubscribe these email addresses. However, hard bounces are either invalid or non-existent addresses that are unsubscribed immediately.

Encharge shows hard bounces as "Bounced". We show soft bounces separately as "Soft bounced".

Soft bounce

A  s_oft bounce_ means that the email address was valid and the email message reached the recipient’s mail server. However, common reasons for a soft bounced back include:

The mailbox was full (the user is over their quota)
The server was down
The message was too large for the recipient’s inbox
Low-quality / spammy email.

With certain transient errors, we continue to attempt to send the emails for up to 72 hours until the email is delivered. If an email is not delivered within 72 hours, it turns into a soft-bounce. Think of soft bounces as blocks that are a short-term issue—you don’t need to permanently take these addresses off of your list.

Hard bounce (shows as "Bounced" in Encharge)

A   hard bounce occurs when the message has been permanently rejected either because:

The email address is invalid
The email address doesn’t exist
The email domain doesn't exist

Continuing to try to send to a known bad address will harm your reputation with the receiver, so we prevent that.  We automatically unsubscribe hard-bounced email addresses. The reason for unsubscribing will be "Email bounced" along with the technical reason for the bounce like this:

What causes an email to bounce back?

There are a variety of reasons that an email message can bounce: the email address doesn’t exist, the inbox is full, server outages, poor sender reputation due to spam complaints, flagged content in the message content, or a restrictive DMARC record for your sending domain.

There are many reasons you receive a delivery status notification that an email bounced (even more than the above list). Those reasons can be temporary — but others are permanent. You will know how to troubleshoot email bounce-backs if you first understand the type of bounce category your email falls under.

1. Blacklisted emails

Email blacklists are created by ESPs (email service providers) to filter harmful or exploitative content, like spam or malware. They don’t exist to make it harder for you to send emails — they exist to protect the recipients of the almost 300 billion emails sent daily.

Why do emails get blocklisted? It usually happens because of:

Spam complaints: The rare complaint is unwelcome but expected. But if complaints reach a certain level, ISPs can send your emails to spam folders or a blocklist.
High bounce rates: If you don’t have good email list hygiene, your bounce rates might start to pile up.
A surge in list size or email volume: If your list grows too fast, it’s a red flag that you may have bought a list. If you start to send massive amounts of emails, it may signal spam and return with an error message.
Bad email content: If you use spammy words in your subject line like “FREE” in all caps followed by 17 exclamation points, stop now.

Being placed on a blocklist can range from being a minor annoyance or it might mean your email campaign is not delivered to any of your subscribers. Large ISPs may have their own blocklists. However, the most popular lists are publicly available and used by email providers and businesses worldwide.

A non-existent email address

If the bounce is marked as “non-existent email address,” the email address could have a typo, or the person with the address may have left the organization. There’s also a chance that the contact gave a false email address, which can be the case if you’re offering something online in exchange for an email.

In this case, it’s important to review the contacts in this category and see if there are any obvious typos in the email address. If not, try to reach the contacts by other means to confirm the address.

2. Undeliverable email

If bounced emails are in the “Undeliverable” category, that means that the receiving email server is temporarily unavailable, was overloaded, or couldn’t be found. A server that can’t be found could have crashed or been under maintenance, so this may just mean waiting to send the email to the address again. However, if this email address repeatedly bounces on multiple emails, it may mean the server is gone for good.

3. Mailbox full

If your contact has so many emails in their inbox that they can’t receive any more, your emails will bounce back until there’s space for them. Sometimes, this can mean that the contact is no longer using that email address.

As with a non-existent email address, you may want to follow up with the contact by social media, phone, or mail to check whether the address is valid.

4. Blocked email

If the email addresses are placed within the “Blocked” category, the receiving server has blocked the incoming email. This is often the case among government institutions or schools, where servers can be more strict when it comes to receiving emails.

To resolve this issue, you need to get in touch with the contact and ask them to Safelist your emails or, when sent to a company address, request that their system administrators unblock Constant Contact’s IP addresses.

How to reduce your email bounce rate

There are several ways to do this and it usually involves list maintenance and good email sending practices.

1. Clean your email list

Identify and remove any unengaged or non-existent email address on a regular basis. Subscribers older than 1 year are at high risk of bounce. Specifically when importing a new list when migrating from another platform, make sure old contacts are removed and all invalid emails archived.

2. Send to Opted - in lists

Only send emails to people who give consent to receive your campaigns. Decide if you want to use a double opt-in email process.

3. Send emails regularly

Send emails to your list often (but not excessively). This leads to fewer spam complaints, higher engagement…and lower bounce rates.

4. User preference center

Give subscribers control over what kinds of emails they get and how often they get them

5. Authenticate emails

Authentication further strengthens your reputation. Verify your domain with SPF, DKIM, and DMARC.

6. Use list segmentation

Segmentation improves your marketing. Email your most engaged customers first. This shows the ESP’s spam filters that you have good content with positive engagement results.

Updated on: 25/03/2025