How accurate are email validation tools for B2B hard bounces?

While email validation tools are highly accurate for basic checks like syntax and known invalid addresses, their accuracy can be limited for B2B catch-all domains. These domains accept all emails at a server level, making it difficult for tools to discern if a specific address is active. They also don't account for sender reputation or content filtering, which can cause hard bounces.

Why is it important to get SMTP bounce reasons from your ESP?

SMTP bounce codes from your ESP provide the precise reason for a delivery failure, such as mailbox full, unknown user, or a server-level rejection (e.g., due to a blocklist listing). This granular data is essential for diagnosing the root cause of a hard bounce, which a validation tool might misinterpret as a 'valid' address if the issue is not related to the address's format or existence.

Should I re-send emails to addresses that a validation tool marks as 'valid' after a hard bounce?

Resending to an address that previously hard bounced, even if a validation tool marks it as 'valid', is risky. If the initial bounce was due to a blocklist (or blacklist) or sender reputation issue, resending could further damage your reputation or lead to your domain being placed on an internal blocklist by the recipient's server.

What are other crucial steps for improving B2B email deliverability?

Beyond validation tools, focus on maintaining a strong sender reputation, implementing SPF, DKIM, and DMARC email authentication, and regularly cleaning your list based on engagement. For B2B, ensure your list is updated to reflect employee changes and that you have proper consent for sending.

Do email validation tools tell me if a B2B recipient is still at a company?

While email validation tools can confirm if an address is syntactically correct and appears to be deliverable, they cannot confirm if an individual is still employed at that company or actively checking that specific email address. For B2B, a 'valid' status doesn't always equate to an 'active and relevant' recipient.

How trustworthy are third party email validation tools for hard bounces in B2B email deployment? - Tools - Email deliverability - Knowledge base

Recently, a client experienced a situation where their B2B email deployment resulted in a significant number of hard bounces. To address this, they used a third-party email validation tool. The tool returned a subset of these previously bounced email addresses as 'Valid'. This immediately raised a critical question: how much trust can we place in these 'valid' results, especially when they contradict prior bounce data from our own email service provider (ESP)?

My immediate thought was to delve into the SMTP bounce reasons directly from the ESP. This information is crucial for understanding the true nature of the delivery failure. While awaiting that data, the client's inclination was to re-send to these supposedly valid addresses. This approach, however, carries significant risks if the underlying issues aren't fully understood.

The trustworthiness of third-party email validation tools for hard bounces in B2B deployment is not as straightforward as it might seem. While these tools offer valuable services in cleaning email lists and reducing overall bounce rates, their interpretation of what constitutes a 'hard bounce' or a 'valid' address can sometimes differ from the reality of email delivery, particularly within complex B2B environments. It's essential to understand their limitations and complement their insights with deeper analytics.

Understanding the limitations of third-party validation tools

Third-party email validation tools primarily operate by performing a series of checks, often including syntax validation, DNS lookups, and SMTP connection tests. For many email addresses, these tests are highly effective at identifying syntax errors, non-existent domains, or obvious invalid addresses. Many tools claim impressive accuracy rates, with some promising 99% email verification accuracy.

However, the B2B landscape introduces a significant challenge: catch-all domains. Many companies configure their mail servers to accept all incoming email for their domain, regardless of the local part (the part before the '@' symbol). These emails are then routed to a central inbox, or simply discarded, but the SMTP server still returns a 'success' message to the sender. This means that a validation tool performing a simple SMTP check will mark such an address as 'Valid', even if the specific recipient address does not exist or the employee has left the company. This is a common source of uncertainty about email validity in B2B contexts.

Understanding catch-all domains

Catch-all domains are prevalent in B2B environments for various reasons, such as ensuring no legitimate emails are missed, facilitating internal routing, or managing historical email addresses. While beneficial for the recipient organization, they pose a challenge for email senders and validation tools because they make it impossible to definitively determine if a specific email address exists or is active through standard SMTP verification. This leads to what we call 'false positives' in validation results.

Beyond catch-all domains, a hard bounce can occur for many reasons that have nothing to do with the email address itself being malformed or non-existent. For example, if your sending IP or domain is listed on a public or private blacklist, or if your sender reputation is low, recipient mail servers might reject your emails, resulting in a hard bounce. This rejection isn't because the address is invalid, but because the server doesn't trust the sender. Third-party validation tools do not typically assess sender reputation or blocklist status, which are critical factors in deliverability.

The importance of ESP bounce reasons

When an email hard bounces, the sending ESP (Email Service Provider) typically provides an SMTP bounce code and a descriptive message. This bounce reason is the most authoritative source of truth regarding why an email failed to deliver. It can indicate if the mailbox truly doesn't exist, if the recipient server is blocking your IP or domain, or if there's a content-related issue causing the rejection.

Relying solely on a validation tool's 'valid' status without checking the ESP's bounce logs means you might be missing the real reason for non-delivery. If the bounce was due to a blocklist (or blacklist) listing or a sender reputation issue, resending to that valid address will likely result in another bounce, further harming your sender reputation and potentially leading to more severe blockages. This is why understanding the causes of bounced emails is so important.

Validation tool reports

Data sources: Primarily rely on SMTP checks, syntax, and DNS records.
Bounce insight: Can detect truly invalid addresses or spam traps, but struggle with catch-all domains.
Actionable steps: Good for initial list cleaning, but not for diagnosing deeper deliverability issues.

To truly address hard bounces, especially in a B2B context, you need a multi-faceted approach. Obtaining the SMTP bounce reasons from your ESP is the first critical step. These codes provide granular detail on the exact reason for the bounce. For instance, a 550 bounce code could mean the mailbox doesn't exist, but it could also mean the recipient's server rejected your email due to a reputation issue or a spam trap hit. Understanding these nuances is key to effective bounce management and improving your overall email deliverability.

Proactive measures for B2B deliverability

Even with the best validation tools, some hard bounces are inevitable, especially in B2B where job changes are frequent. The goal is not zero bounces, but a manageable bounce rate that doesn't harm your sender reputation. A common benchmark for hard bounce rates after validation is often aimed below 5%. This is why proactive measures are more effective than relying solely on post-bounce validation.

Implementing strong email authentication protocols like SPF, DKIM, and DMARC is fundamental. These protocols help recipient servers verify that your emails are legitimate and prevent spoofing. Consistent enforcement of these standards can significantly improve your deliverability and reduce the likelihood of your emails being rejected outright, regardless of whether the specific address exists or not. Many resources are available to help you set up DMARC, SPF, and DKIM.

The sender's perspective

Authentication issues: Poorly configured Microsoft 365 or Google Workspace settings can cause rejections.
Domain reputation: A compromised or low-reputation domain will face delivery challenges.
Content issues: Spammy keywords or poor formatting can trigger filters.

The recipient's perspective

Catch-all setup: Many B2B domains accept all mail, making specific address validation difficult.
Internal routing: Even if accepted, the email might not reach the intended inbox.
Recipient filters: Personal or corporate filters can move emails to spam.

A clean email list starts with proper consent and ongoing hygiene. For B2B, this means regularly updating your database to account for job changes and ensuring that your email acquisition methods gather genuinely interested and valid contacts. While validation tools are part of this, they are not the sole solution. Focus on maintaining a strong sender reputation and understanding the granular details of your bounces for effective deliverability.

The ongoing value of validation tools

Even with their limitations regarding hard bounces on catch-all domains or non-address-related issues, third-party email validation tools remain valuable. They excel at identifying syntactically incorrect addresses, disposable email addresses, and known spam traps, which if mailed to, could severely damage your sender reputation and lead to you being on a blocklist (or blacklist).

They act as a crucial first line of defense, helping to reduce the overall bounce rate by catching the most straightforward invalid addresses before they even leave your ESP. This initial cleaning step is vital for maintaining good sender health. Remember, while a tool can tell you an address is 'valid' in a technical sense, it cannot tell you if the recipient actually exists or if their server will accept your email based on your sender reputation or content.

For B2B marketing, it's wise to use these tools for bulk and real-time validation, but always couple their results with your ESP's bounce logs for any hard bounces. This combined approach provides the most accurate picture of your email list's health and ensures you're addressing the root causes of delivery failures, protecting your email program for the long term. These tools are often part of a suite of recommended email validation tools.

Views from the trenches

Best practices

Always retrieve and analyze SMTP bounce codes from your ESP to understand the specific reason for email delivery failures.

Implement and maintain robust email authentication (SPF, DKIM, DMARC) to improve sender reputation and prevent rejections.

Regularly segment and clean your email lists, especially B2B lists, to remove inactive or departed contacts.

Monitor your sender reputation using Postmaster Tools and other monitoring services.

Prioritize explicit consent for email collection to build a highly engaged and resilient list.

Common pitfalls

Assuming a 'valid' status from a third-party tool means guaranteed deliverability, especially for B2B catch-all domains.

Ignoring ESP bounce logs and re-sending to addresses that hard bounced for reasons other than invalid syntax.

Focusing solely on email validation as the only solution for deliverability issues, neglecting sender reputation and authentication.

Not understanding the difference between a user unknown bounce and a blocklist-related bounce.

Sending to old, unengaged B2B lists without prior re-engagement campaigns or validation.

Expert tips

For B2B, consider supplementing email validation with CRM data or LinkedIn checks to verify current employment.

If you suspect catch-all domains, a strategy of low-volume, high-value sends can help identify truly active recipients.

Use email validation tools for bulk cleaning, but rely on real-time bounce processing for new sign-ups.

Combine validation with A/B testing on content and sending practices to optimize for deliverability.

Regularly review your email sending practices against current industry best practices and ISP requirements.

Expert view

Expert from Email Geeks says that no one knows more about your mail than you or your ESP. You need to understand why the mail failed to deliver and address that before mailing again.

2024-01-26 - Email Geeks

Expert view

Expert from Email Geeks says that your ESP, IP, or domain might be blocked, which is why seeing the actual bounce reason is crucial. Valid addresses do not guarantee deliverability if the initial cause of failure is unknown.

2024-01-26 - Email Geeks

Achieving true deliverability in B2B

The trustworthiness of third-party email validation tools for hard bounces in B2B email deployment is high for identifying common syntax errors and truly non-existent domains. However, for addresses within catch-all domains or bounces caused by sender reputation, blocklists, or content issues, their 'valid' assessment should be treated with caution. They are a valuable component, but not the sole arbiter of deliverability.

For optimal B2B email deliverability, combine the insights from validation tools with detailed bounce data from your ESP. Prioritize a strong sender reputation, maintain robust email authentication, and actively manage your lists based on consent and engagement. This holistic approach ensures your messages reach their intended recipients, even in the nuanced landscape of B2B email.