You’ve just sent out your email campaign. The statistics start to come in and then, surprise: some of your emails never reached their destination. The report shows “bounces”. Some are described as “hard”, others as “soft”. And you wonder what this means in concrete terms for your next mailings.
These bounces aren’t just a line in your statistics. They tell us something about the health of your contact base and the perception e-mail providers have of you as a sender. Understanding the difference between hard bounce and soft bounce gives you the means to take action before your deliverability deteriorates permanently.
Hard bounce: when the email is definitively rejected
A hard bounce is a permanent rejection. Your e-mail will never reach this address, no matter how many times you try. The receiving server has answered categorically: this address does not exist or is no longer accessible.
Mail servers communicate with each other via response codes. A hard bounce generally results in a code of type 5XX, signifying a definitive error. The receiving server refuses to accept the message and will not reverse its decision.
There are several situations that can lead to a hard bounce. The email address contains a typo, which is more common than you might think. The account has been deleted by its owner or by the email provider after a long period of inactivity. The domain name no longer exists or has been deactivated. In some cases, the receiving server permanently blocks your domain or IP address because it considers you undesirable.
Authentication failure can also generate a hard bounce. If your SPF, DKIM or DMARC records are misconfigured, some servers will refuse your emails outright. This technical problem has become more frequent since Gmail and Yahoo tightened their requirements in February 2024.
Soft bounce: a temporary problem that can be solved
The soft bounce is different. The address does exist, the server has recognized it, but the message could not be delivered this time. This is a temporary failure.
Soft bounce response codes are generally of type 4XX. The server indicates that it cannot process the request now, but that a subsequent attempt may be successful.
The recipient’s inbox is full. It’s a classic, especially when someone goes on vacation without having set up an automatic reply. Emails accumulate until they reach saturation point. The recipient’s mail server is experiencing a temporary technical problem or is undergoing maintenance. Your email is too large and exceeds the limits accepted by the server. The content of your message has triggered a spam filter, but the server is giving you a chance to correct it.
Most emailing platforms automatically make several attempts to send the message when they receive a soft bounce. If after several attempts, generally between three and five, the message still fails to arrive, the address is treated as a hard bounce.
The fundamental difference between the two types of bounce
The distinction is simple, but the consequences are far-reaching. A hard bounce means that the address is definitively unusable. A soft bounce indicates a one-off problem that may disappear.
| Features | Hard bounce | Soft bounce |
|---|---|---|
| Type of problem | Permanent | Temporary |
| Possibility of recovery | No | Possible after resolution |
| Recommended action | Immediate deletion | Monitoring and retries |
| Impact on reputation | Strong and immediate | Moderate if recurrent |
In your campaign reports, the two types of bounces are generally distinguished. This separation allows you to adopt the right strategy for each category. Deleting a hard bounce is obvious. For a soft bounce, the decision depends on its recurrence.
Why bounces damage your reputation as a sender
Messaging providers keep a close eye on sender behavior. Every campaign you send helps build your reputation. A high bounce rate sends a negative signal: you’re not properly maintaining your contact base.
According to the Validity Email Deliverability Benchmark 2024 report, around one in six emails never reaches its recipient’s inbox. The overall inbox placement rate is around 84%. Bounces contribute directly to this wastage.
In fact, Gmail tightened its policies during 2024. The inbox placement rate on Gmail fell from 89.8% at the start of the year to 87.2% in the fourth quarter, following the implementation of new requirements for bulk senders.
Beyond a 2% bounce rate on a campaign, your deliverability starts to deteriorate. ISP spam filters take this rate into account when deciding whether to accept your next mailings. A high proportion of hard bounces can lead servers to consider your messages as spam. And once this label has been applied, it’s hard to get rid of.
Bounce rates vary according to your business sector
Not all sectors are equal when it comes to bounces. Mailchimp data from December 2023, based on the analysis of billions of emails, reveals significant discrepancies.
The construction sector has the highest hard bounce rate at 1.28%. At the other end of the scale, coupon and bargain sites achieve only 0.13%. E-commerce stands at 0.57%, travel and transport at 1.02%.
These differences are partly explained by address collection practices. Some sectors collect contacts via well-designed online forms with double opt-in. Others have been accumulating addresses for years without ever cleaning them up. The quality of the base is directly reflected in the bounce rate.
The B-to-B sector generally has slightly higher rates than B2C. Business addresses change more often: departures, job changes, company mergers. An address that was valid six months ago may well have disappeared since then.
Best practices for reducing your bounces
Removing hard bounces from your lists immediately is non-negotiable. Continuing to send emails to addresses that no longer exist will damage your reputation without any possible benefit. Your emailing platform should handle this automatically, but check regularly to make sure it does.
For soft bounces, adopt a differentiated approach. An isolated soft bounce is not dramatic. On the other hand, if an address generates soft bounces over three or four consecutive campaigns, it’s time to consider it a hard bounce and remove it from your list.
Double opt-in remains the best defence against bounces. By asking each new contact to confirm their registration via a validation email, you eliminate typos and fanciful registrations. Yes, you lose a few contacts who won’t confirm. But the ones that remain are of real quality.
Validate email addresses as soon as they are collected. Real-time verification tools can detect syntax errors, non-existent domains or disposable addresses before they even enter your database. It’s an investment that quickly pays for itself.
Cleaning up your e-mail database regularly should be part of your routine. At least once a quarter for active bases. Addresses that never open your e-mails for more than a year deserve a re-engagement campaign. If they still don’t respond, delete them.
The technical configuration of your sending domain is no longer optional. SPF, DKIM and DMARC must be correctly configured. Since February 2024, Gmail and Yahoo require these authentications for senders of more than 5,000 emails per day. Even below this threshold, correct configuration will improve your deliverability.
Maintaining a healthy foundation: a profitable investment
Managing bounces is not an administrative constraint. It’s a performance lever for your email campaigns.
A clean base means a better deliverability rate. A better deliverability rate means more recipients actually receive your messages. And more messages received mechanically means more opens, more clicks, more conversions.
Emailing platforms generally charge by the number of contacts or the volume sent. Keeping invalid addresses in your database means paying for nothing. Worse, it’s paying to damage your reputation.
List hygiene is not an exciting subject. Nobody gets up in the morning thinking they’re going to have a great day cleaning up their contact database. But it’s this in-depth work that makes the difference between average and excellent deliverability. Between campaigns that reach the inbox and campaigns that end up as spam.
Frequently asked questions about bounces
WHAT IS AN ACCEPTABLE BOUNCE RATE FOR AN EMAIL CAMPAIGN?
A bounce rate of less than 2% is considered acceptable. Below 1%, your database is in excellent health. Above 2%, it’s time to investigate and clean up your contact list to avoid deliverability problems.
SHOULD YOU DELETE A CONTACT AFTER A SINGLE SOFT BOUNCE?
No, an isolated soft bounce does not justify deletion. Wait and see if the problem recurs. After three to five consecutive soft bounces on different campaigns, you can consider the address a hard bounce and remove it.
HOW DO I KNOW IF MY BOUNCE RATE IS DUE TO A TECHNICAL PROBLEM?
If your bounce rate rises sharply on a campaign when it was previously stable, first check your technical configuration. A problem with SPF or DKIM authentication can cause massive rejections. Check the detailed error codes in your platform’s reports.
DOES DOUBLE OPT-IN REALLY REDUCE BOUNCES?
Double opt-in virtually eliminates hard bounces due to data entry errors and false addresses. It’s the most effective way of ensuring that every address in your database is valid and belongs to someone who wants to receive your communications.
HOW OFTEN SHOULD YOU CLEAN YOUR CONTACT DATABASE?
Quarterly cleaning is the minimum for an active base. If you send out very frequent campaigns, or if your base evolves rapidly, a monthly check is preferable. Remember also to clean up before each major campaign.
DO BOUNCES PERMANENTLY AFFECT MY REPUTATION?
No, sender reputation is built over time. A few campaigns with a high bounce rate may temporarily worsen your score, but by improving your practices, you can gradually build it back up. Consistency in list hygiene is the key.
WHY ARE MY EMAILS BOUNCING OFF ADDRESSES THAT USED TO WORK?
Business addresses have a limited lifespan. If an employee leaves a company, his or her address is often deleted. Inactive personal accounts can also be closed by e-mail providers. That’s why regular cleaning of your database is essential.
