Email Health Check: How to Audit Your Email Program Before Deliverability Suffers

You don’t need an email deliverability crisis to benefit from an email health check. Learn how to evaluate your email list, sender reputation, authentication, engagement, and deliverability before small issues turn into major problems.

For most people, email is part of their daily routine from the moment they wake up until they go to bed. Maybe that describes you, too. 

A ZeroBounce study found that the average person checks their email dozens of times a day, including on vacation and during even the most private of moments. Few marketing channels offer close to the kind of consistent access that email does. 

But simply sending out emails? That’s not enough. Getting your emails into the inbox consistently depends on much more than writing a great message and clicking Send. 

Many businesses don’t realize something is wrong with their email marketing until bounce rates increase or engagement dips. By then, recovering sender reputation can take weeks or even months. 

What is an email health check?

An email health check helps you identify issues before they affect your email deliverability. It evaluates the key factors that influence whether your messages reach the inbox, from email list quality and sender reputation to authentication, engagement, and sending practices.

No single metric can tell you whether your email program is healthy. To get the full picture, you need to evaluate multiple factors working together. 

Many marketers think an email health check begins and ends with cleaning their email list. In reality, that’s just one piece of the puzzle. 

As ZeroBounce CMO Anne Ghaltchi explains:

“Email health is more than just cleaning your email address list to remove invalid and other risky email addresses. It includes ongoing monitoring and proactive steps to maintain deliverability and engagement over time to make sure your messages actually land in the inbox.”

So what does a complete email health check look at?

• Email list quality
• Sender reputation
• Authentication
• Engagement
• Sending practices
• Your “from” name (sender identity)

Let’s look at each of these areas in more detail. 

Step 1. Audit your email list health

Your email list is the foundation of your email marketing. No matter how compelling your emails are, they can’t perform well if you’re sending them to invalid, outdated, or disengaged contacts.  

Every business has its own email strategy, one principle is universal: a healthy email list is essential for strong deliverability and engagement. 

Here’s how to assess your email list. 

Check your bounce rate

Your bounce rate can tell you a lot about the health of your email list. 

There are two types of email bounces. A hard bounce means the email couldn’t be delivered permanently, usually because the address is invalid or no longer exists. A soft bounce is temporary and can happen because the recipient’s mailbox is full, the server is unavailable, or the message is too large.

As a general rule, you should aim to keep your bounce rate below 2%. Consistently exceeding that threshold is often a sign that your email list needs attention. 

A high bounce rate tells mailbox providers that your email list may not be well maintained. Too many bounces can hurt your sender reputation and make it more difficult for future emails to reach the inbox. 

Are you getting too many bounces? Clean your email list

Remove invalid and inactive email addresses

Email addresses have a shelf life – think bread instead of wine. Even the healthiest email list naturally degrades over time as people change jobs, abandon accounts, or stop using certain email addresses. 

The best way to keep your list healthy is to validate it regularly, not just when you notice a problem. Regular bulk email validation helps you identify invalid, inactive, and other risky email addresses so you can remove them before they affect your deliverability. 

The other major component of email hygiene is ensuring that your freshly scrubbed list isn’t infected with bad data anyway. All of your forms are vulnerable to bad emails. The solution is to connect an email validation API to prevent contamination. This will stop harmful email addresses at the source. 

Watch for spam traps

Spam traps are one of the fastest ways to damage your sender reputation, so they’re an important part of any email health check. 

Spam traps usually look like ordinary email addresses, but they’re monitored by mailbox providers and anti-spam organizations to identify senders with poor list hygiene. The idea is simple: legitimate senders shouldn’t be emailing addresses that have been abandoned or were never intended to receive email.

Some spam traps are simply recycled email addresses that were abandoned and later repurposed to try and trick spammers. Some spam traps never belonged to a real person at all.

Hitting spam traps can tank your sender reputation, get you blacklisted, and affect your inbox placement. The best way to avoid spam traps is to maintain a permission-based email list, validate your contacts regularly, and remove inactive subscribers before abandoned addresses become spam traps.  

Identify disposable email addresses

Disposable email addresses are another threat to a healthy email list. They’re created for people who don’t want to share their real email address. But while many disposable email addresses are valid when they’re created, they often disappear shortly afterward. 

Your email validation platform should be able to identify disposable emails. Just because they get a green checkmark that they’re ready to receive mail doesn’t mean they always will. 

The moment that mailbox is deleted, it’s bounce time. Blocking disposable email addresses helps keep your email list healthier and reduces unnecessary bounces over time. 

Review how new contacts are added

Take a close look at where your email addresses are coming from. Review your signup forms, lead magnets, and any individual employee lists you import to ensure you’re attracting real, engaged subscribers.

Make sure all of your team members know that new email addresses are always validated before use. One person on the sales team with a lackadaisical attitude about email hygiene can hurt your entire domain or company.

If your team is using purchased or third-party contact lists, review them carefully before sending. These lists may contain outdated email addresses, inactive contacts, or even spam traps. More importantly, make sure you’re only emailing people who have given the appropriate consent to receive your messages and validate the addresses before adding them to your database. 

Every new contact should have a clear path into your database and meet the same standards for quality and permission as the rest of your list. Pause and consider any contact you make with a new user. 

Step 2. Review your email authentication

Email authentication is a set of protocols that proves your emails are really coming from your domain. It helps mailbox providers distinguish legitimate messages from spoofed or fraudulent ones.

Today, proper email authentication isn’t optional. Mailbox providers like Google and Yahoo require senders to authenticate their domains to help protect users from phishing and email spoofing. Without these protocols in place, your emails are far less likely to reach the inbox. 

The good news is that setting up email authentication is easier than it used to be, and many email deliverability platforms now offer tools and guidance to simplify the process.

Here are the key authentication protocols every sender should understand.

Check your SPF record

Your SPF (Sender Policy Framework) record tells mailbox providers which servers are allowed to send email on behalf of your domain. If the SPF record is missing or configured incorrectly, your emails are likely to fail authentication or be rejected.

Review your SPF record regularly, especially when you add a new email service or provider, and make sure it includes every platform authorized to send email on behalf of your domain. 

Verify your DKIM is configured correctly

DKIM (DomainKeys Identified Mail) adds a digital signature to your emails and helps mailbox providers confirm that your messages are really from you and haven’t been altered in transit.

Review your DKIM configuration regularly and rotate your DKIM keys at least every six months. Rotating keys is a security practice that helps protect your domain if a key is ever compromised. 

Be sure the DKIM is set up correctly, because if it isn’t, your emails could be treated with suspicion. Check that it’s properly configured for every platform you use to send email.

Review your DMARC policy

DMARC (Domain-based Message Authentication, Reporting & Conformance) builds on SPF and DKIM to inform mailbox providers how to handle email that fails authentication. DMARC also gives you reports that can help you spot unauthorized use of your domain.

Review your DMARC policy regularly, especially when you add new email services or change your sending infrastructure. A properly configured DMARC record helps protect your domain from spoofing while protecting your email deliverability.

Learn how to secure your domain with DMARC

Step 3. Check your sender reputation

A strong sender reputation gives your emails the best chance of landing in the inbox instead of the spam folder. Think of it as a credit score for your email program: the better your reputation, the more mailbox providers trust your messages.

Start by monitoring your domain reputation and, if you send from a dedicated IP, your IP reputation as well. Google Postmaster Tools is a great place to start. It offers insights into your reputation, spam rates, authentication, and other Gmail deliverability metrics. 

There’s also Microsoft SNDS (Smart Network Data Services), which shows your reputation for Outlook and Hotmail addresses.

Finally, keep a constant focus on your spam complaint rate. Every time someone marks your email as spam, it sends a negative signal to mailbox providers. If complaints begin to climb (higher than 0.1%), review your list quality, email frequency, and content to identify what’s turning recipients away. The lower your complaint rate, the healthier your sender reputation will be.

Step 4. Evaluate your email engagement

If there’s one thing you should always keep top of mind, it’s this: mailbox providers always know how people react to your emails.

It’s this simple: positive engagement tells them your messages are wanted. What about negative engagement or indifference? That will always hurt your inbox placement over time.

As part of your email health check, review these key engagement metrics:

• Open rate: Open rates can still help you identify broad trends, but they’re no longer the reliable metric they once were. Privacy features such as Apple Mail Privacy Protection can inflate opens, so avoid using open rate as your primary measure of success. Instead, look at it alongside clicks, spam complaints, unsubscribes, and other engagement metrics. 
• Click-through rate (CTR): Measures how many recipients clicked a link in your email. Low click-through rates can suggest your content, offer, or calls to action need improvement.
• Click-to-open rate (CTOR): Unlike CTR, CTOR measures clicks only among people who opened your email. It’s a useful way to evaluate how engaging your email content is after the open.
• Spam complaint rate: This is one of the most important metrics to monitor. Aim to keep your complaint rate below 0.1%, and never let it reach 0.3%, the threshold used by Gmail and Yahoo for bulk senders. High complaint rates can quickly damage your sender reputation.
• Unsubscribe rate: Some unsubscribes are perfectly normal and even healthy—they’re far preferable to spam complaints. However, a noticeable increase may signal that your content, sending frequency, or audience targeting needs attention.

Metric	What to aim for
Spam complaint rate	Below 0.1% (never 0.3% or higher)
Bounce rate	Below 2%
Unsubscribe rate	Typically below 0.2–0.5%
Click-through rate (CTR)	Compare against your historical average and industry benchmarks
Click-to-open rate (CTOR)	Compare against your historical average and industry benchmarks
Open rate	Use for long-term trends only. Don’t rely on it as a standalone metric because privacy protections can inflate opens.

Tip: Don’t judge your email program based on a single campaign. Instead, look for trends over time. One email may perform unusually well or poorly, but consistent patterns provide a much more accurate picture of your email program’s overall health. 

Step 5. Review your sending practices

If your email list is healthy and subscriber engagement is good, what can go wrong? As it turns out, plenty.

Even the best email programs can suffer from inconsistent sending habits, poor targeting, or sending too many emails. 

Sending schedule

Evaluate your sending frequency. You never want to badger people with your emails, but you also don’t want people to forget all about you. This is where knowing your brand becomes so critical. 

For example, an author may send two emails a month, or even just one. But some industries send daily emails – take stock or finance-oriented newsletters where people want to know what is happening every day.

Figuring out your sending schedule is the easy part. Sticking to it consistently is where many senders struggle. But sending your emails on time is a great way to maintain deliverability. 

What if you need to really crank up your email marketing? Like, if you’re going to send more emails during the holiday season? In that case, slowly increase your volume so that it doesn’t trigger any alarms from email service providers (ESPs).

Tip: Create a checklist for every campaign. Review your schedule, timing, email copy, links, and graphics before you send. That will help you stay consistent and avoid mistakes. 

Segment your audience

Not all of your subscribers want the same thing. That’s why you segment your audience based on interests, purchase history, or engagement so you can send more relevant emails.

The more catered your campaigns are, the more likely people are to open, click, and stay subscribed. Segmentation dials up relevance. 

Personalize your emails

Personalization goes beyond using someone’s first name. Use the data you have to send relevant content, recommendations, and offers based on each subscriber’s interests and behavior. Just be sure to personalize thoughtfully – incorrect or overly aggressive personalization can do more harm than good.

At its best, personalization feels like a personal email. At its worst, it feels like a template that was generated with your name thrown in. That distinction matters: a ZeroBounce study showed that 46% of people regularly open emails from brands that consistently send them valuable, relevant messages.  

Make sure every subscriber has opted in

Send emails to people who have explicitly agreed to hear from you. This means using the double opt-in method: someone must click a generated link that gets sent to the email they provided. This way, they had to perform at least one simple action to confirm their interest. 

Sending to non-opted-in contacts will lead to more spam complaints and lower engagement, which can damage sender reputation. So it’s best to build a permission-based email list to protect your deliverability and the relationship you have with your subscribers. 

This is not an area where you should skimp. In fact, adding additional safeguards will work in your favor. Luke Glasner, Director of Deliverability at ZeroBounce, advises you to also take action to thwart bots from attacking your forms. 

“Secure your forms with things like a CAPTCHA because the amount of bot sign-ups and form attacks I have seen in the past two to three years has exponentially grown.”

Step 6. Check your email infrastructure

You’d be surprised how easily small technical issues can slip into your email program. A broken link, outdated template, or misconfigured setting can go unnoticed for weeks or even months.

Your technical setup plays an important role in deliverability and overall success. That’s why it’s smart to review the following regularly:

Test for broken links

Few things frustrate subscribers more than clicking a link that goes nowhere. Oftentimes, they don’t search for a workaround and just give up on you altogether. Before every campaign, test each link to make sure it works and leads to the correct destination.

Check tracking links

If you use UTM parameters or click tracking, verify that everything is working properly. Broken tracking can leave you with inaccurate campaign data and make it impossible to accurately measure results.

Test landing pages

Your email is only half the experience. Make sure every landing page loads quickly, matches the email’s message, and makes it easy for visitors to take the next step. It’s happened to most people – you click a link only to find that the landing page in question is incongruent. 

Optimize for mobile devices

More than 60% of people read email on their phones instead of the computer. Preview every campaign on mobile, tablet and desktop to ensure your text is readable, buttons are easy to tap, and images display correctly.

Monitor email loading speed

Large images and bloated code can slow down your emails. Keep your design lean and mean. Optimize your assets so your messages load quickly, especially for someone with a slower connection.

Test your deliverability for free

Warning signs your email program needs a health check

A healthy email program doesn’t become unhealthy overnight. More often, small issues appear gradually, and that gives you time to identify and fix them before they affect your deliverability.

Watch for these warning signs:

• Bounce rates are increasing. This is a major warning sign. If bounces are up, something is askew. Clean your list and remove all outdated and invalid contacts.
• Spam complaints are rising. If email had a medical comparison, this would be like experiencing shortness of breath. Rising spam complaints are the most serious indicator that you’ve made a misstep or your list needs serious attention.
• Emails are landing in spam folders. This is bound to happen sometimes, but if you’re landing in spam your emails don’t have a chance. You’ve got a deliverability problem and an email health check can pinpoint the issue.
• Subscriber engagement has dropped. Having some ebb and flow is normal. If you’ve got a seasonal product, you may have times where you’re red hot and others where you’re not. If engagement doesn’t pick up, it could be an email health issue.

If engagement drops after changing email service providers 

Switching email service providers (ESPs) can introduce deliverability challenges if the migration isn’t planned carefully. Email marketers sometimes find themselves in diagnostic mode, trying to figure out why metrics suddenly declined. 

Many companies assume they can switch ESPs and pick up right where they left off. Not so fast, according to Ciprian Vlad, Enterprise Success Manager at ZeroBounce.

“It’s like leaving a house you lived in for years and moving to a new one. You know the neighborhood, your utility providers, and your neighbors inside and out. You have long-term relationships with all of them. But once you move, you need to start completely from scratch.”

Just as you’d reconnect your utilities after moving, email marketers need to make sure the essentials are configured correctly before sending. That means checking SPF, DKIM, and DMARC, confirming everything is working properly, and verifying that the new sending environment is fully set up.

Ciprian Vlad encourages businesses making the switch to ask themselves one important question:

“Have I spent enough time building trust with my domain for the new infrastructure?”

Building up trust takes time.

“Let’s say you moved to Constant Contact,” Ciprian Vlad explained. “You need to start building again, so send in low volumes initially. Make sure you have engagement, then increase the volume by keeping an eye on results.”

In other words, establish a history of positive sending before ramping up your email volume. Deliverability problems rarely happen without warning. 

“And if something happens, it’s never out of the blue,” Ciprian Vlad said. Instead, investigate what changed recently that may have affected your deliverability.

For many organizations, the challenge is finding the time to manage every part of a migration. “Companies often don’t have the resources to make sure they do everything that needs to be done,” Ciprian Vlad noted.

That’s why preparation matters. Rather than treating an ESP migration like flipping a switch, plan ahead. Verify your authentication, warm up your sending little by little, and monitor your results closely. As Ciprian Vlad puts it, “It’s important to think and act on all of this prior to going with a new ESP.”

Related: Ciprian Vlad of ZeroBounce on What Every Email Marketer Should Know About Deliverability

Why you should perform regular email health checks 

Regular email health checks help you spot small issues before they become deliverability problems. Because so many factors influence whether your emails reach the inbox, reviewing your email program on a consistent basis is one of the best ways to protect its long-term performance. Since email is one of the few marketing channels you truly own, it’s worth keeping it in top shape.

Regular email audits can help you:

• Protect your sender reputation by identifying issues before they affect deliverability.
• Improve inbox placement so more of your emails reach subscribers instead of the spam folder or not being delivered at all.
• Reduce bounce rates by maintaining a clean, up-to-date email list.
• Increase engagement and conversions with more relevant, better-performing campaigns.
• Catch problems early before mailbox providers or subscribers notice them.

A little preventive maintenance can save you weeks of troubleshooting later. 

How often should you perform an email health check?

An email health check isn’t something you do once and forget about. Some tasks should be part of every campaign, while others only need attention every few months. Here’s a simple schedule to follow. 

Task	Recommended frequency
Validate your email list	At least quarterly (or before every major campaign)
Monitor blacklist status	Continuously with blacklist monitoring (or manually at least monthly)
Review engagement metrics	After every campaign
Review bounce and spam complaint rates	After every campaign
Audit SPF, DKIM, and DMARC	Quarterly (and after infrastructure changes)

Email health checklist

Use this checklist as part of your regular email maintenance. A quick review can help you identify issues early and keep your email program performing at its best. Bookmark this page whenever you need a quick email health check. 

• Validate your email list
• Remove invalid and inactive contacts
• Review your SPF, DKIM, and DMARC records
• Review your sender reputation
• Monitor your blacklist status
• Review your engagement metrics
• Review your audience segmentation
• Review your sending schedule and consistency
• Test your email infrastructure
• Verify your inbox placement
• Monitor your spam complaint rate

Should you use an email health check tool?

You can perform many email health checks manually, but keeping track of everything over time can eat up a lot of time. Using a dedicated deliverability platform makes it much easier to monitor your email program consistently and respond before problems creep up.

Finding a platform that brings your email health data together in one place will help you streamline everything. You no longer have to piecemeal several email optimization platforms out there. Ideally, you can find a service that offers the following:

• Validate your email list to remove invalid, risky, and low-quality addresses.
• Monitor blacklists so you know if your domain or IP has been listed.
• Check email authentication by monitoring your SPF, DKIM, and DMARC records.
• Track sender reputation and other signals that influence inbox placement.
• Monitor deliverability to see where your emails are landing and identify potential problems.
• Review email activity and engagement to better understand how recipients interact with your campaigns.

Rather than juggling multiple subscriptions and tools, many senders prefer an all-in-one platform that combines these capabilities into a single dashboard. 

For example, ZeroBounce One brings together email validation, blacklist monitoring, DMARC monitoring, deliverability testing, inbox placement tests, and email activity data, making it easier to keep your email program healthy without constantly switching between different applications.

You can find a service that offers all of these features in one place, so you’ll get a more accurate assessment of your email health.

The goal is to identify issues early or even before they arise, so you can maintain a strong sender reputation and consistently reach the inbox.

Need a platform that can do it all? Try ZeroBounce One

Make email health a go-to habit

A healthy email program doesn’t happen by accident. Great email marketing combines compelling content with consistent maintenance. 

• The first part is connecting with your audience authentically. This means good copy and design. It also means making a human connection. You can’t outsource everything to AI and be done with it. Good email marketers roll their sleeves up.
• The other part is consistently maintaining your email list, monitoring your sender reputation, using solid email authentication, and paying attention to how people engage with you.

The good news is that you don’t have to master all of these things all at once. Start with the basics: validate your email list, authenticate your domain, and keep an eye on the metrics. 

From there, make email health checks a regular habit. A little preventative maintenance today can save you from the headache of asking: what is going on with my emails?

Whether you manage email on your own or as part of a larger team, you have to treat email health as an ongoing process. When you make it as much a part of your job as the creative side, you’ll reach more inboxes and get satisfying results.