Table of Contents
- What is an Email Deliverability Audit and Why is it Important?
- Signs You Need an Email Deliverability Audit
- How to Conduct an Email Deliverability Audit
- 1) SPF (Sender Policy Framework)
- 2) DKIM (DomainKeys Identified Mail)
- 3) DMARC (Domain-based Message Authentication, Reporting & Conformance)
- 4) Identify Blacklist Issues & Spam Traps
- 5) Review Your Sender Reputation
- 6) Optimize Email Content & Formatting
- 7) Clean Your Email List
- 8) Monitor Sending Behavior & Rate-Limiting
- 9) Test Inbox Placement
- 10) Warmup
- 11) Custom Tracking Domain
- 12) Separate Domain for Cold Email
- 13) Dedicated vs. Shared IPs
- 14) PTR (Reverse DNS) Record
- 15) Custom Return-Path & Bounce Handling
- 16) Ongoing Monitoring & Maintenance
- Conclusion
- FAQs
- 1. What are the most common email deliverability issues?
- 2. How to test email deliverability?
- 3. How can I improve my sender reputation?
- 4. Why do my emails land in the Gmail Promotions tab instead of the inbox?
- 5. How often should I clean my email list?
Sending an email is easy.
But making sure it actually gets delivered in the inbox? That’s a different story.
There’s a whole system working behind the scenes—filters, authentication checks, sender reputation scores—all deciding whether your email reaches the inbox.
If you’re not paying attention to these factors, you’re leaving deliverability to chance.
That’s why an email deliverability audit is essential. It’s not about guesswork—it’s about checking the right settings, analyzing your sending practices, and making sure nothing is quietly working against you.
In this guide, I’ll walk you through a step-by-step audit to review your setup, catch potential email deliverability issues, and improve your deliverability. Let’s get into it.
What is an Email Deliverability Audit and Why is it Important?
An email deliverability audit digs into what’s really happening with your emails—whether they’re landing in inboxes, getting lost in spam, or not showing up at all. If email is a key part of your outreach, sales, or customer engagement, knowing where your messages are going (or not going) is essential.
Even if your emails land in the inbox for you, email service providers (like Gmail and Outlook) analyze dozens of factors before deciding whether to deliver them, send them to spam, or block them entirely. An audit helps you uncover hidden issues that could be hurting your deliverability, such as:
- Authentication Failures – Missing or misconfigured SPF, DKIM, or DMARC can make your emails look suspicious.
- Reputation Problems – If your IP or domain has a poor reputation, email service providers might be rejecting your emails.
- Spam Triggers – Certain words, formatting, or sending patterns can make your emails look like spam. Check out 832+ email spam trigger words that gmail is blocking in 2025.
- Engagement Drops – Low open and click rates tell providers that recipients don’t find your emails relevant, which can push future emails to spam.
- Technical Issues – Problems with email headers, sending infrastructure, or bounce handling can silently damage deliverability.
Without an audit, you won’t have a clear picture of how ESPs are treating your emails. Even if they’re being sent, email deliverability issues could mean they aren’t consistently reaching recipients’ primary inboxes.
Signs You Need an Email Deliverability Audit
If you’re sending emails but not seeing the results you expect, your deliverability might be suffering. Here are the key signs that it’s time for an audit:
1. Your Open Rates Have Dropped
If fewer people are opening your emails, it’s a red flag. Low open rates can mean your emails are landing in spam folders or not reaching inboxes at all.
2. You’re Getting More Spam Complaints
Recipient spam reports signal email service providers to filter your future emails. One clear indication that something’s gone awry is a spike in complaints.
3. Your Bounce Rate Is Rising
A high hard bounce rate (because emails are permanently undeliverable) will hurt your sender reputation, while an increase in soft bounces (temporary delivery failures) can indicate a serious problem with your email setup.
4. Emails Are Going to Spam More Often
If contacts tell you they found your email in their spam folder, you need to investigate. Email service providers don’t send emails to spam randomly—there’s always a reason.
5. Engagement is Declining
Are people opening but not clicking? Are replies dropping? Low engagement tells email service providers that your emails might not be relevant, which can hurt your sender reputation.
6. You’re Sending From a New Domain or IP
If you recently switched email providers, changed domains, or started sending from a new IP, you need to warm up your sender reputation. Otherwise, email service providers might flag your emails as suspicious.
7. You Haven’t Checked Your Authentication Setup
If your SPF, DKIM, or DMARC records are missing or incorrect, your emails might not be getting properly authenticated—which can make them look like phishing attempts.
8. You’re Not Sure About Your Email List Quality
Using old, purchased, or scraped email lists increases the risk of sending to invalid addresses, spam traps, or people who never opted in—leading to bounces and complaints.
If any of these sound familiar, an email deliverability audit isn’t optional—it’s necessary. The sooner you identify the problem, the faster you can fix it and get your emails back into inboxes.
How to Conduct an Email Deliverability Audit
Before diving into the detailed steps, grab this Email Deliverability Audit Guide in an easy-to-follow Excel format. Download it now and start optimizing your email deliverability today!
1) SPF (Sender Policy Framework)
SPF confirms whether your emails are sent from an authorized server, helping prevent spoofing and phishing attempts.
How to check? Use tools like EasyDMARC to analyze SPF records.
Solution: Ensure all authorized mail servers are listed in your SPF DNS record, and avoid multiple SPF records, as this can cause validation failures.
2) DKIM (DomainKeys Identified Mail)
DKIM ensures that your emails haven’t been tampered with during transmission by attaching a cryptographic signature to your messages.
How to check? Use tools like EasyDmarc, Google Postmaster, MXToolbox to verify DKIM signatures.
Solution: Ensure your email provider has DKIM signing enabled and that your public DKIM key is correctly published in your DNS settings.
3) DMARC (Domain-based Message Authentication, Reporting & Conformance)
DMARC builds on SPF and DKIM to provide policies that help prevent domain spoofing and phishing attempts.
How to check? Use EasyDMARC or Google Postmaster to monitor DMARC policies.
Solution: Configure a DMARC policy that aligns with SPF and DKIM and gradually move from p=none to p=quarantine or p=reject to enforce security. If your authentication settings are misconfigured, email providers like Gmail and Outlook may reject or flag your emails as spam.
4) Identify Blacklist Issues & Spam Traps
If your emails aren’t reaching inboxes, your domain or IP may be blacklisted due to spam complaints, high bounce rates, or sending to spam traps.
How to check? Run your domain through a blacklist lookup tool like MX Toolbox.
What to do if blacklisted?
- Find out why (spam traps, complaints, excessive bounces).
- Improve list hygiene (remove invalid emails, and clean inactive subscribers).
- Request delisting from the blacklist provider after fixing the issue.
5) Review Your Sender Reputation
Email providers track your sender reputation based on engagement (opens, clicks, replies) and complaints.
How to check? Use tools like Google Postmaster to track spam complaints and domain reputation.
Red Flags:
- Spam rate above 0.1% = Risk of emails being filtered.
- Spam rate above 0.3% = Emails may be blocked altogether.
Solution: If complaints rise, adjust your sending frequency, refine audience targeting, and ensure emails are relevant and properly formatted.
6) Optimize Email Content & Formatting
Even if your email setup is perfect, your content could still trigger spam filters.
How to check? Use an email testing tool like Mail Tester to analyze spam triggers.
Best Practices:
- Avoid spam words like “free,” “limited-time offer,” or “guaranteed.”
- Use a good text-to-image ratio (avoid image-only emails).
- Ensure a clear CTA without aggressive salesy language.
- Avoiding Spammy Headers & Tracking Links
7) Clean Your Email List
Poor email list hygiene leads to high bounce rates and spam traps, damaging your reputation.
How to check? Use an email verifier like Sparkle.io to categorize emails as Safe, Unsafe, or Unknown.
High bounce rate? If it’s above 0.3%, your list needs cleaning.
Solution:
- Remove invalid or inactive emails regularly.
- Use double opt-in to prevent fake sign-ups.
- Monitor engagement and re-engage inactive subscribers.
8) Monitor Sending Behavior & Rate-Limiting
Email providers flag suspicious sending patterns, which can lead to rate-limiting.
How to check? Use an email tracking tool to monitor sending volume and engagement trends.
Red Flags:
- Sending spikes (e.g., 50 emails one day, 500 the next).
- Low engagement despite high volume.
Solution:
- Gradually increase sending volume (warm-up process).
- Space out emails instead of bulk sending.
- Do not exceed 50-100 emails/day per inbox for cold outreach.
- Rotate between multiple sending times to avoid patterns.
9) Test Inbox Placement
Even if your emails are sent, they might not land in the Primary Inbox.
How to check? Use an inbox placement tool like Sparkle.io to see where emails land (Inbox, Spam, Promotions).
Why are emails going to spam?
- Authentication failures (SPF, DKIM, DMARC not set up correctly).
- Low engagement or high spam complaints.
- Too many images, links, or “salesy” words.
Solution: Optimize formatting, personalize emails, and monitor engagement trends.
10) Warmup
If you’re sending mail from a new domain — or one that has been dormant for a while — the quickest way to raise red flags with email service providers is to go straight into high-volume sending.
Email algorithms are always on the lookout for suspicious behavior, and an abrupt increase in volume for a non-credible domain can damage your deliverability.
A proper warmup gradually builds your sender reputation, signaling to email providers that your emails are legitimate and engaging—not spammy.
Best Practices for a Smooth Warmup:
- Start Slow and Scale Gradually – Begin with a small number of emails and increase volume steadily over a few weeks. This allows email providers to recognize your domain as a trustworthy sender.
- Track Key Metrics – Keep an eye on open rates, spam complaints, and bounce rates. If engagement drops or complaints spike, slow down and adjust your sending strategy.
- Avoid Sudden Volume Surges – Rapidly increasing email volume can trigger spam filters. Consistency is key to staying in good standing with email service providers.
11) Custom Tracking Domain
Using a custom tracking domain is a simple yet powerful way to improve email deliverability. Instead of relying on shared tracking links from email providers—many of which are overused and flagged as spam—you can maintain control over your sender reputation with a branded domain. This not only enhances credibility but also reduces the risk of landing in spam folders.
How to Set It Up:
- Use a Branded Domain – Replace generic tracking links with a custom domain that aligns with your brand. This keeps your emails looking professional and trustworthy.
- Enable HTTPS Tracking Links – Secure your tracking URLs with HTTPS to prevent security warnings and build trust with recipients.
- Monitor Your Domain Reputation – Use tools like Google Postmaster Tools to track your domain’s health and catch any deliverability issues early.
With a custom tracking domain, your emails are less likely to be flagged as spam, giving you better inbox placement and improving overall campaign performance.
12) Separate Domain for Cold Email
Using your primary business domain for cold email campaigns is a risky move. Cold outreach naturally sees lower engagement, and if too many emails go unopened or marked as spam, your domain’s reputation takes a hit. That’s why it’s best to keep cold emails on a separate domain.
Why Use a Separate Domain?
- Reduces Blacklisting Risk – Cold email can trigger spam filters, and a separate domain keeps your main one protected.
- Keeps Core Emails Safe – Your marketing and transactional emails won’t be affected by the lower engagement rates of cold outreach.
- Easier Performance Monitoring – Separating domains helps track and adjust different email strategies without harming your brand’s overall email performance.
It’s a simple way to protect your sender reputation while running cold email campaigns effectively.
13) Dedicated vs. Shared IPs
The choice between a dedicated or shared IP plays a big role in email deliverability, especially for high-volume senders. If your IP reputation takes a hit, your emails might never reach the inbox.
How to Check Your IP Reputation? Use tools like Sender Score to see how your IP is performing and whether it’s flagged as risky.
Solution:
- Sending Large Volumes? A dedicated IP gives you full control over your reputation, but it needs to be warmed up gradually to avoid spam filters.
- Using a Shared IP? Make sure your provider actively manages the reputation and enforces best practices—since one bad sender can affect everyone.
IP Pool Management:
- Dedicated IPs – Keep an eye on volume distribution to prevent sudden spikes that can raise red flags.
- Shared IPs – Always check who else is using the same IP to ensure you’re not sharing space with spammy senders.
Choosing the right IP setup helps maintain a strong sender reputation and improves inbox placement.
14) PTR (Reverse DNS) Record
PTR (Reverse DNS) records verify that your sending IP corresponds to your domain, which is essential for email authentication.
How to check? Use MXToolbox or leaseweb.com to confirm your PTR records.
Solution:
- Ensure your PTR record matches your sending domain to prevent authentication failures.
- If using multiple sending domains, configure separate PTR records for each IP.
- Work with your hosting provider or email service to correct any misconfigurations.
15) Custom Return-Path & Bounce Handling
The Return-Path plays an essential role in processing bounces and protecting sender reputation.
How to check? Use Google Postmaster Tools or your email provider’s settings to verify Return-Path configuration.
Solution:
- Ensure your Return-Path domain aligns with your sender domain for accurate bounce tracking.
- Set up a dedicated bounce handling system to categorize bounces (soft, hard, and spam complaints).
- Regularly review bounce logs and adjust sending strategies accordingly.
16) Ongoing Monitoring & Maintenance
Email deliverability isn’t a “set it and forget it” process. Regular audits prevent small issues from turning into major problems.
How often should you audit?
- Every 3-6 months for standard email marketing.
- Monthly audits if sending cold emails or high-volume campaigns.
- Daily monitoring for bounce rates, spam complaints, and blacklist status.
Quick Tip: Set up automated monitoring for key metrics and schedule audits based on risk factors.
Conclusion
We’ve covered everything—from authentication settings to sender reputation to optimizing your email-sending patterns. But here’s the thing: email deliverability isn’t a one-time fix.
Email service providers constantly tweak their algorithms, and even small missteps can quietly hurt your email placement over time. That’s why regular audits and smart sending practices aren’t just best practices—they’re non-negotiable.
So before you hit send on your next campaign, ask yourself:
- Is my domain properly authenticated?
- Am I sending at a pace that maintains a strong reputation?
- When was my last deliverability check?
The brands that consistently land in the inbox aren’t the ones who fixed deliverability once and forgot about it. They’re the ones who make it part of their routine.
So take a moment, audit your setup, and refine your strategy. Because when your emails land where they should, every send becomes an opportunity—not a gamble.
FAQs
1. What are the most common email deliverability issues?
Common email deliverability issues include emails landing in spam, authentication failures (SPF, DKIM, DMARC), blacklisting, high bounce rates, and poor sender reputation due to low engagement or spam complaints.
2. How to test email deliverability?
You can test email deliverability using inbox placement tools, blacklist checkers, and email authentication tests to see if emails reach the inbox, spam, or promotions folder across different providers.
3. How can I improve my sender reputation?
To improve your sender reputation, ensure SPF, DKIM, and DMARC are correctly configured, maintain a clean email list by removing invalid and inactive addresses, and focus on increasing engagement by sending relevant content. Monitoring your reputation using Google Postmaster Tools can help track spam complaints and domain health.
4. Why do my emails land in the Gmail Promotions tab instead of the inbox?
Gmail categorizes emails based on content, sender behavior, and recipient engagement. Emails with multiple links, images, and marketing-style wording are more likely to be filtered into the Promotions tab. To increase the chance of landing in the Primary inbox, personalize your emails, use minimal formatting, and avoid excessive sales language.
5. How often should I clean my email list?
Regular list hygiene is crucial for deliverability. If you’re sending high-volume emails or cold outreach campaigns, monthly cleaning is recommended. For general marketing emails, every 3-6 months should be sufficient. Always remove hard bounces immediately and re-engage inactive recipients before removing them.
