How to Effectively Monitor Email Deliverability & Inbox Placement
Mastering the Monitoring of Email Deliverability & Inbox Placement: Take Control, Track the Right Metrics, and Ensure Your Emails Hit the Inbox!
Introduction
In one of our recent posts, 12 Ways to Improve Your Email Deliverability and Inbox Placement, we shared practical #tips to ensure your emails get delivered & land in your audience's inboxes - all with examples of what those tips did for one of our clients.
But what comes next, you may ask?
The next step should be —> consistent & strategic monitoring.
After implementing initial Deliverability Best Practices, proactive monitoring helps you identify “small issues” before they escalate into “big problems”. Email Marketing is a very dynamic landscape, ISPs frequently update spam filtering algorithms as well as their inbox categorization, and user behavior continually evolves. To stay ahead, you need continuous visibility into what's happening after you hit "Send." The advantage is, that destroying your reputation usually happens gradually - not after one hiccup.
In this guide, we dive deeper into:
What email deliverability monitoring truly involves.
How inbox placement differs and why you need to track it separately.
Which key metrics matter the most.
Essential tools and methodologies for effective monitoring.
So, without further ado - let’s jump straight into it!
Understanding the Difference: Email Deliverability vs. Inbox Placement
Here a quick refresher for the terms in question:
Email Deliverability —> Refers to the successful delivery of emails to recipient mail servers. This indicates your email wasn't rejected or bounced by the ISP (Gmail, Outlook, Yahoo, …). High deliverability typically means you're successfully reaching the mailboxes, but it doesn’t guarantee the correct inbox.
Inbox Placement —> Specifically refers to whether your emails appear in the recipient’s primary inbox, secondary tabs (promotions or updates), or the spam folder. Even with strong deliverability, poor inbox placement can severely limit engagement.
Monitoring both independently ensures you're not just reaching your audience, but actually making meaningful contact!
Monitoring Email Deliverability: Metrics & Tools
Long-term success in this areas relies mainly on proactively tracking & monitoring of key metrics and adapting to any shifts in performance.
Following Metrics should be calculated & monitored closely, ideally directly in your ESP:
Delivery Rate % —> The percentage of emails successfully accepted by recipients mail servers. Aim for 98% - 99%+. Lower delivery rates may indicate issues with your sender reputation, list hygiene, or the broader technical setup.
Soft Bounce Rate % —> The percentage of emails temporarily undeliverable due to temporary deliverability (e.g.: full inboxes, temporary server outages, bulk sends / sending too quickly, etc.). Keep this rate below 0.5%. Regularly monitor patterns to proactively address recurring problems - if necessary, take action on specific error codes/messages if they express a high % of your bounces.
Hard Bounce Rate % —> The percentage of emails permanently undeliverable due to invalid or non-existent email addresses. Maintain this rate below 0.3%. High hard bounce rates signal poor list hygiene and should be handled with high attention.
Spam Complaint Rate % —> The percentage of recipients marking your emails as spam/junk. Ensure this rate stays below 0.1%. Even minor increases (going to 0.3%) can temporary send your emails to the spam folder - as we have experienced firsthand.
In this case, the principle "more is better" applies - a good Email Service Provider (ESP) should offer you as much information as possible. Ideally, this includes not only aggregated data but also detailed insights into specific campaign performance for each metric, enabling you to make informed decisions on how to improve. Flexibility goes a long way, the more information each bounce includes (specific error codes, messages, etc.), and the more freedom you have to handle each of them individually, the better.
Essential Deliverability Monitoring Tools
Even though monitoring the above with given baselines should be possible in the majority of ESPs, to get an additional advantage on this front we strongly recommend subscribing directly to monitoring services provided by major ISPs - they are usually free. These tools significantly enhance your visibility into and understanding of your email performance, particularly regarding those specific mailbox providers (but you can always extrapolate to others). Below are the most essential ISP-specific tools - but if a significant portion of your subscriber base uses another ISP - we advise checking whether that provider offers a similar service:
Google Postmaster Tools —> Provides insights into your domain’s sending reputation (IP & Subdomain), delivery errors, spam complaints, and others specifically for Gmail recipients.
Microsoft SNDS (Smart Network Data Services) —> Delivers detailed data on your IP’s sending reputation, email volume, spam reports & spam-trap hits, and delivery performance within Microsoft’s ecosystem (Outlook, Hotmail, Live, etc.).
There are also additional tools you can leverage here - these come with a price tag. What we found is, however, that the above is enough on this front. Additional tools can enhance your understanding - but might not be worth it if you have no deeper issues with the metrics above.
Monitoring Inbox Placement: Strategies & Tools
Now, let’s shift our focus specifically to inbox placement - this one is a trickier and a more nuanced component to track.
Mailbox providers use complex, evolving algorithms based on user engagement signals (opens, clicks, replies, forwarding, mark as read, marking emails as spam or important, …). A message successfully delivered but consistently placed in Promotions or Spam folders significantly reduces visibility and impact.
Following Metrics are important:
Inbox Placement Rate % —> The percentage of your delivered emails landing directly in primary inboxes versus promotions, updates, or spam folders. For this you will probably need an additional tool.
Engagement Rates % by ISP —> Observe variations in open/click rates by mailbox provider (Gmail, Outlook, Yahoo). Low engagement with a specific provider usually signals inbox placement issues specific to that ISP. This you should still be able to see in your ESP - have a “baseline” of open/click rates % for specific mailbox providers & set-up notifications if you detect anomalies (= unexplainable drops in engagement metrics).
Seed Testing Results —> Regularly perform seed-list tests (= sending test emails to inboxes across multiple providers) to simulate real-world inbox placement and troubleshoot any potential email problems. Don’t always trust tools - but see how you perform for yourself!
Essential Inbox Placement Monitoring Tools
GlockApps (free & paid) —> Tool offering real-time inbox placement testing, allowing you to see whether your emails land in the inbox, spam, or promotions folder across major ISPs. Also, it provides detailed spam filter testing, authentication checks (SPF, DKIM, DMARC), sender reputation monitoring, and others.
ZeroBounce (free & paid) —> Offers inbox placement testing to analyze how different mailbox providers categorize your emails. Additionally, it specializes in email validation, helping you clean your list by identifying invalid, spam-trap, or low-quality addresses before sending.
Validity (Everest) (paid) —> Provides advanced deliverability monitoring, inbox placement testing, and reputation tracking. The Everest platform combines real-time performance monitoring, blacklist checks, and sender score analysis to help businesses optimize email performance - they include a lot in the product (in most cases more than you will need), but also don’t offer a free plan to test.
Mailgun (paid) —> While primarily a transactional ESP, they also offer email validation and reputation tracking tools and support inbox placement tests as well - amongst other things.
!Ask your ESP! —> Some ESPs offer this service as well - so always feel free to reach out to your point-of-contact & just ask them, most of the times they will be able to direct you to some partner.
How To Guide: Implementing an Effective Monitoring Strategy
Now - after the theory heavy part - let’s translate it into practice, a step-by-step guide:
1. Establish a “Baseline”
Before starting monitoring, establish a “baseline” for your key metrics (deliverability rates, hard/soft bounces, spam complaints, inbox placement, etc.). This baseline helps you quickly detect anomalies.
2. Set Up Daily/Weekly Monitoring Checks (Notifications?)
Ideally, create a consistent schedule to review key metrics daily/weekly if they differ from your set baseline by big margins. If you have no notifications set-up, a quick review can also spot emerging issues early, allowing swift corrective action.
Shout out to our #5 Must-Have Notification! Why do it manually, when you can have a real-time alerts in place for this?
3. Conduct Regular Seed Tests
You can do this with every Newsletter, but at least once per month, perform an inbox placement seed test across major providers of your subscriber base (Gmail, Outlook, Yahoo). Actively monitor your placement.
4. Monthly Reputation Audits
Use free tools like Google Postmaster Tools and Microsoft SNDS monthly to verify your sender reputation and swiftly address any dips. Mostly follow your IP & Subdomain reputation, but keep an eye out on your spam rates as well.
5. Quarterly Deep Dives
Every quarter, deeply analyze email engagement metrics (opens, clicks, complaints, unsubscribes) segmented by mailbox providers. Identify patterns to proactively adjust your strategy. Run your Inbox Placement Tests at least once per quarter to know how you are performing with placement.
Conclusion: Stay Ahead with being Proactive!
As also previously mentioned, Email marketing is ever-changing. What works today might change tomorrow. Implementing systematic monitoring for email deliverability and inbox placement isn't just a best practice - it’s essential for sustainable marketing performance.
At E3, we believe in enabling & empowering marketers not just with knowledge but actionable strategies to elevate their results. The practices outlined above aren't simply recommendations, they're proven pathways to protecting your reputation, maximizing engagement, and driving results.
Stay vigilant, stay informed, and continue refining your approach with the learnings above.
Ready to Dive Deeper?
If you're ready to elevate your email marketing strategy further, feel free to reach out to our team at E3. We're always here to help you unlock your full potential!