What are the best practices for email verification and reducing bounces?
Michael Ko
Co-founder & CEO, Suped
Published 23 Apr 2025
Updated 15 Aug 2025
9 min read
High email bounce rates are a clear indicator that something is amiss with your email marketing strategy. Not only do they prevent your messages from reaching their intended recipients, but they also severely damage your sender reputation, leading to lower deliverability and potentially even blacklisting (or blocklisting, if you prefer). Effectively managing bounces and implementing robust email verification practices are crucial for maintaining a healthy email program and ensuring your messages land in the inbox.
Understanding the different types of bounces, and more importantly, why they occur, is the first step toward a solution. Many times, the issue isn't just about cleaning a list, but rather addressing underlying problems in how email addresses are acquired and managed. I've seen countless instances where a proactive approach to email hygiene and verification could have saved businesses significant headaches and lost revenue. Let's delve into the best practices that can help you reduce bounces and improve your email deliverability.
The importance of email verification
Email verification is the process of confirming that an email address is valid and deliverable. It's a critical step in maintaining email list hygiene. Ignoring this can lead to a high bounce rate, which signals to internet service providers (ISPs) and email service providers (ESPs) that you might be sending to old, invalid, or improperly collected addresses, thus harming your sender reputation.
I often emphasize that the best time to verify an email address is at the point of collection, right when a user signs up. This real-time validation prevents bad data from entering your system in the first place, saving you time and resources down the line. It's much more efficient to stop a problem at its source than to try and fix it after it has already impacted your email metrics.
Regularly cleaning your existing email list is equally important. Even with the best acquisition practices, email addresses can become invalid over time as people change jobs or abandon old accounts. A periodic scrub, especially before large campaigns, ensures you are only sending to engaged and valid recipients. This process significantly reduces hard bounces, which are particularly damaging to your sender reputation.
Hard bounces occur when an email is permanently undeliverable, typically due to an invalid or non-existent email address. These are the most damaging type of bounce because they strongly indicate poor list quality and can quickly lead to your IP address or domain being added to a blocklist (or blacklist). For instance, if you're sending to an address like nonexistent@example.com, it will hard bounce every time. You can find out more about email bounce rates to understand their impact.
Soft bounces are temporary delivery failures, meaning the email is valid but couldn't be delivered for a specific reason. Common causes include a full inbox, server issues, or the recipient's mail server temporarily blocking your message. While less severe than hard bounces, a high volume of soft bounces can still indicate problems with your sending practices or recipient engagement. It's often worth investigating the reasons behind frequent soft bounces, as some (like those from Gmail or Microsoft) can sometimes indicate a user complaint.
Monitoring your bounce reports is crucial to distinguish between hard and soft bounces. Hard bounces should be immediately removed from your list to protect your sender reputation. For soft bounces, it's advisable to re-attempt sending a few times, but if they persist, consider segmenting or removing those addresses, especially if they show no engagement. Understanding how bounces impact deliverability is key.
Hard bounces
Indicate permanent delivery failures, such as invalid or non-existent email addresses. They significantly damage your sender reputation and should be removed from your list immediately. If your hard bounce rate is consistently above 0.5-1%, it's a red flag indicating a serious problem with your list acquisition or hygiene practices.
Remove immediately: Any address that hard bounces should be permanently removed from your mailing list.
Impact on reputation: High hard bounce rates negatively affect your sender score and deliverability.
Soft bounces
Represent temporary delivery issues, such as a full inbox or a server being down. While less critical than hard bounces, repeated soft bounces from the same address can also indicate an underlying problem with deliverability or engagement. You can learn more about cleaning up soft bounces.
Retry strategy: Most ESPs automatically retry sending soft-bounced emails over a period.
Monitor and manage: If an email soft bounces consistently, consider removing it or re-engaging the subscriber.
Preventative measures and list hygiene
One of the most effective ways to ensure list quality is to implement a double opt-in process for new subscribers. This requires users to confirm their subscription via an email link after signing up, verifying that the email address is valid and that the user genuinely wants to receive your communications. This proactive step dramatically reduces hard bounces and helps avoid spam traps.
You should regularly cleanse your email list to remove inactive or unengaged subscribers, along with hard bounces. This isn't just about removing invalid addresses, but also about improving overall engagement metrics. Sending to disengaged recipients can lead to lower open rates, higher complaint rates, and eventually impact your sender reputation, making it harder to reach active subscribers. This is why some marketers will advise you to use activity data instead of verification services.
Additionally, ensure your signup forms are secure and not susceptible to bot attacks or list bombing. Implementing measures like CAPTCHAs or reCAPTCHAs can prevent automated systems from submitting fake or malicious email addresses to your list. I've seen many cases where a sudden spike in bounce rates was traced back to unprotected signup forms. You can find out more about email validation on sign-up.
Point of collection validation
Implementing email verification at the point of signup ensures that invalid or fake email addresses never make it onto your list in the first place.
Real-time email validation examplejavascript
/* Example JavaScript for real-time validation (simplified) */
function validateEmail(email) {
// Simulate API call to email verification service
const regex = /^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$
return regex.test(email);
}
document.getElementById('emailInput').addEventListener('blur', function() {
const email = this.value;
if (!validateEmail(email)) {
document.getElementById('emailError').innerText = 'Invalid email address';
} else {
document.getElementById('emailError').innerText = '';
}
});
Regular list cleansing
Even with real-time validation, lists degrade over time. Regularly cleaning your list removes addresses that have become invalid or inactive since their initial signup. This also involves identifying and removing spam traps (or honeypots), which are email addresses used by ISPs to catch senders with poor list hygiene. Landing on a spam trap list can lead to your emails being blacklisted or blocked.
Email authentication protocols play a vital role in ensuring your emails are trusted by recipient servers and don't end up bouncing due to suspicious origins. Implementing SPF, DKIM, and DMARC validates that your emails are legitimately coming from your domain, reducing the likelihood of them being flagged as spam or spoofing attempts.
DMARC, in particular, allows you to tell receiving servers what to do with emails that fail SPF or DKIM checks (e.g., quarantine or reject them), and provides valuable DMARC reports from Google and Yahoo that offer insights into your email stream. This visibility helps you identify issues that might be leading to bounces or other deliverability problems.
Monitoring your sender reputation is an ongoing task. Tools like Google Postmaster Tools provide feedback on your sending performance, including spam rates, IP reputation, and domain reputation. A consistent high bounce rate or an increase in spam complaints will be reflected here, giving you early warnings to adjust your strategy before significant damage occurs. Remember, improving your email deliverability is an ongoing effort that involves many factors beyond just email verification.
Protocol
Purpose
Impact on bounces
SPF
Authorizes specific senders to send emails on behalf of your domain.
Reduces bounces from unauthorized sending, which might otherwise be seen as spoofing.
DKIM
Adds a digital signature to emails, verifying content integrity and sender identity.
Prevents bounces due to email tampering or forging during transit.
DMARC
Provides policy control over emails that fail SPF/DKIM and offers reporting.
Allows you to enforce policies that prevent unauthenticated emails from reaching inboxes, thereby reducing fraudulent traffic that could lead to bounces and blacklisting.
Content and sending practices
In addition to technical measures, your content and sending practices significantly influence bounce rates. Avoid using purchased email lists at all costs. These lists are notorious for containing high percentages of invalid, inactive, and spam trap addresses, which will instantly tank your sender reputation. Focus on building a permission-based list through organic sign-ups.
Your email content should always be relevant and engaging to your audience. Irrelevant content leads to low engagement, high unsubscribe rates, and increased spam complaints, which can indirectly contribute to bounces. A high complaint rate can cause ISPs to filter your emails or even soft bounce them due to poor sender reputation, even if the address is valid. It's also worth noting that list hygiene is important.
Finally, ensure that your unsubscribe process is clear and easy to find. Forcing users to jump through hoops to unsubscribe can frustrate them and lead to spam complaints instead. A clean list with engaged subscribers is always preferable to a large, unverified list that generates bounces and complaints.
Views from the trenches
Best practices
Implement a double opt-in process for all new email sign-ups to confirm subscriber intent and email validity.
Integrate real-time email verification on all your signup forms to catch invalid addresses before they enter your database.
Regularly clean your email list, removing hard bounces, unengaged subscribers, and any suspected spam traps.
Monitor your email authentication (SPF, DKIM, DMARC) and sender reputation metrics diligently.
Segment your audience and personalize content to improve engagement and reduce spam complaints.
Common pitfalls
Purchasing or renting email lists, which are often filled with invalid addresses and spam traps.
Neglecting to remove hard-bounced addresses, which severely damages your sender reputation.
Not using double opt-in, leading to lower quality lists and higher bounce rates.
Having insecure signup forms vulnerable to bot submissions and list bombing.
Ignoring engagement metrics, as low engagement can lead to soft bounces and filtering.
Expert tips
Look beyond just bounce rates, analyze the specific reasons for soft bounces, as some can indicate user complaints or filtering.
Focus on the underlying processes that lead to poor list quality rather than just trying to clean a bad list.
Consider using activity data as a primary indicator of list health over sole reliance on verification services.
If using verification services, understand their limitations, especially regarding soft bounces due to complaints.
Maintain a consistent sending volume and pattern to build a reliable sender reputation with ISPs.
Marketer view
Marketer from Email Geeks says BriteVerify and Kickbox are often recommended, but ensuring subscribers actually want your emails is most important.
2020-08-10 - Email Geeks
Marketer view
Marketer from Email Geeks says to investigate the root cause of bounces, such as bounce reasons, list age, and subscriber acquisition methods, before resorting to list cleaning services.
2020-08-10 - Email Geeks
Summary: Building a robust email program
Effective email verification and bounce reduction are foundational to strong email deliverability. It's not just about running your list through a checker once; it's about embedding these practices into every stage of your email program, from subscriber acquisition to ongoing list maintenance and reputation monitoring. By taking a comprehensive approach, you can significantly reduce your bounce rates, protect your sender reputation, and ensure your messages consistently reach the inbox. Continuous vigilance and adaptation to evolving email landscapes are key to long-term success.
Remember that a healthy email list is an engaged email list. Prioritize quality over quantity, and your efforts will pay off with improved inbox placement and better campaign performance. Regularly cleaning and verifying your email addresses is an investment in your sender reputation and the overall effectiveness of your email marketing strategy.
Gmail or 
Microsoft) can sometimes indicate a user complaint.
Google Postmaster Tools provide feedback on your sending performance, including spam rates, IP reputation, and domain reputation. A consistent high bounce rate or an increase in spam complaints will be reflected here, giving you early warnings to adjust your strategy before significant damage occurs. Remember, improving your email deliverability is an ongoing effort that involves many factors beyond just email verification.
