How to Run an Email Deliverability Test in 30 Minutes

You don’t need a full-time deliverability consultant on your staff to keep your emails hitting inboxes. You can keep your reputation high and emails out of spam in just 30 minutes.

These regular audits are critical because you’ll be able to diagnose dips in deliverability before they kill your engagement. 

This guide will show you a simple 30-minute playbook with free or low-cost tools along with exact strategies.

Why You Need Deliverability Checks 

Even if you’ve nailed your email setup, you still need to check in occasionally to make sure everything’s running smoothly.

Engagement Rates Are a Symptom, Not the Cause

It’s an easy logic-leap for newsletter operators to attribute dropping engagement to content issues or an old list.

However, more often, worsening engagement is a signal that something else is going wrong—and it’s usually an inboxing issue. This is especially the case if you’ve had good engagement in the past, and it’s recently tapering off.

With a deliverability check, you can diagnose the behind-the-scenes issues and fix them before your bottom line is affected.

Keep an eye out for:

• Declining open rates
• Higher spam rates
• Bounce spikes

You should think of these like a check engine light coming on. It’s time to dig deeper and find what’s actually happening here.

Early Detection Saves Sender Reputation

All mailbox providers (e.g., Gmail, Apple Mail) have distinct algorithms for tracking your domain’s sending behavior.

If your sender reputation takes a hit, these mailbox providers are less likely to deliver your emails to inboxes. 

And, much like a check-engine light, things get worse if you ignore them!

If your subscribers who use Gmail start opening & clicking less, that’s eventually going to spread to Outlook, Yahoo, and others. They may have separate algorithms, but they’re each fairly similar in what they’re looking for.

The 30-Minute Email Deliverability Test

Plan regular intervals—like once a week or month—and schedule it on your calendar. It’s worth every second.

Step 1: Check Your DNS Authentication

In theory, these should be a one-time setup, but it’s not always that simple. Perhaps you’ve switched or added a sending domain and forgot to update your authentication. Or, maybe you want to update your DMARC protocol.

Or, most commonly, someone on your team changed a setting in your DNS setup, and now your authentication protocols aren’t aligned.

With a tool like MXToolbox, you can easily check:

• SPF
• DKIM (you’ll need your DKIM selector. Your email software can tell you what it is, or find the “s=” tag in the header of your email)
• DMARC

If you pass all three of these, your emails are authenticated and ready to send!

Step 2: Run a Spam Test

Take a recent newsletter and run it through a test like mail-tester.com. For free, it’ll give you a score out of 10, with lower numbers equating to a higher likelihood of going to spam folders.

Here are a few common red flags that lower your score:

• Overly promotional subject line
• URL shorteners (common spam tactic) or broken links
• Too many images for the amount of text
• No plain-text version (most legitimate senders include this and is a signal checked by mailbox providers)

In a perfect world, you’d run every email through a spam check, but at the very least, include this in your regular audit.

Step 3: Test Inbox Placement

Testing inbox placement is often overlooked by email senders, or it’s something they check once and never again.

With a tool like GlockApps, you can send a test email to inboxes they maintain across several mailbox providers. Then, you can see whether your emails go to spam, Primary, Promotions, or are undelivered altogether. 

Here’s a quick rule of thumb for deliverability metrics (according to Mailtrap):

Step 4: Audit Engagement Metrics By Mailbox

It’s likely you’re regularly tracking the usual suspects: opens, clicks, unsubscribes, and some type of conversion metric (appointments, sales, etc.).

However, you should regularly be going deeper to non-surface level issues, such as engagement by mailbox provider.

Earlier we mentioned how each mailbox has their own algorithm, and sender reputation issues often cross over from one to another.

That means it’s of the highest importance to quickly uncover when engagement drops with one of them. It’s a great indicator that it’s a deliverability issue, and not a content one (or else it’d affect all your subscribers).

Many email software will allow you to sort by mailbox provider, or you can export the list and manipulate an Excel spreadsheet.

Step 5: Review List Health

You should regularly be removing (or attempting to reengage) leads that aren’t engaging with your emails.

In other words, any subscribers who haven’t opened or clicked within a predetermined amount of time should be filtered out. This timeframe could be 30, 60, or 90 days, or based on a number of sends.

Within some email software, you can set this all up ahead of time, and even have them enter a re-engagement campaign. If they don’t engage with that campaign, then they’re unsubscribed.

If you don’t have the option to do this automatically, you should still be able to quickly generate a list of unengaged subscribers. Then, you can send them an email or two, or just unsubscribe them on the spot.

Removing unengaged leads is a simple path to increasing engagement across the board.

Step 6: Consider Content & Subscriber Expectations

It’s easy to stray away from your core brand & promise in the name of trying new things. It’s also easier to identify this has happened by reviewing your last several sends.

Are you still delivering what your subscribers want and what you promised? Are you sending at the same cadence? Have you strayed to being more salesy in the name of hitting revenue metrics? 

If you promised once-a-week emails and start sending daily, you’ll have higher unsubscribe & spam rates, hurting your sender rep.

Now, consider the content within each email for the following:

• Visible Unsubscribe Links - You want to make it easy for people to leave your list. It’s both an easy way to clean your list and avoids spam complaints from those who can’t unsubscribe with ease.
  
  
• Consistent links - If a link in your email says yourbrand.com but takes you to an eBay affiliate link, that looks spammy to mailbox providers.
  
  
• Engaging Content - Try adding polls, surveys, bullet points, and charts. Write short, skimmable sections to keep readers more engaged to the end.
  
  
• Avoid Spammy content - Avoid sounding gimmicky, overly promotional, or fake. Also, these 188 words have been proven to trip spam filters.

Step 7: Check Google Postmaster Tools

As a free tool, Google Postmaster Tools shows your email health based on Gmail’s algorithm. 

You’ll see a graph over time that shows:

• Spam Rate
• IP Reputation
• Domain Reputation
• Feedback Loop
• Authentication
• Encryption
• Delivery Errors

Much of this data is available elsewhere, but it’s free and simple to check. 

Step 8: Run a Blacklist Check

It’s a simple one, yet very important:

Using a tool like MXToolbox, you can see if your domain has been added to any blacklists. In addition, it’ll give you instructions for how to remove your domain from the list.

How to Interpret and Fix Your Results

If you’ve been generally on top of your deliverability, you (hopefully) won’t find much wrong with each audit. 

Here’s how to handle the results you find:

• Green Across the Board - If everything looks good, congrats! Don’t forget to keep your audit on your calendar and perform every 2-4 weeks. Maybe without any fires to put out, you can finally get around to improve something you’ve been thinking about.
  
  
• 1-2 Issues - Depending on the issue, it’s likely a quick-fix opportunity (such as too many images or a DMARC problem). Don’t delay, as deliverability will only get worse.
  
  
• Red Flags - It’s probably time to pull back severely on the emails you’re sending, do a full audit, and reassess everything. You may need to resort to more severe fixes, such as performing a full warm-up cycle and implementing double opt-in.

Frequently Asked Questions

How often should I run a deliverability check? At minimum, you should run through this deliverability checklist each month. However, if your business relies heavily on email, you might need to check every 1-2 weeks to catch any issues that could severely hurt revenue. Also, you might consider a deliverability check before sending any critical emails.

Do I need paid tools to run a deliverability audit? No. Tools like MXToolbox, Mail-Tester, Google Postmaster Tools, and basic inbox testing accounts are free or low-cost. Paid tools like GlockApps offer deeper insights but aren’t required to get started.

What are the most common causes of poor deliverability? Typically, sendes with deliverability issues are running into one (or more) of these issues:

• Missing or misaligned SPF, DKIM, or DMARC
• High number of unengaged subscribers
• Spammy content or broken links
• Too many images, no plain-text version
• Sending too frequently or straying from expected content

Won't removing unengaged subscribers hurt my list size? Yes, but you're removing subscribers who are no longer interested. By taking them off your list, you'll improve deliverability, opens, and ultimately, revenue. List size is a bit of a vanity metric—you'd do better to focus on conversions.

How long does it take to fix bad deliverability? Minor issues can be solved in hours (like fixing a DMARC record). Severe problems—like spam folder placement or domain blacklisting—may take weeks and require list cleaning, warm-up cycles, and reduced sending.