Have you ever sent an important email campaign only to discover that many of your subscribers never received it? You're not alone. Email deliverability issues affect businesses of all sizes, but the good news is that most problems can be fixed with the right approach.
Email deliverability refers to the ability of your emails to successfully reach your subscribers' inboxes rather than getting lost in spam folders or being blocked entirely. When your deliverability suffers, so does your entire email marketing strategy.
In this guide, we'll walk through practical steps to identify and fix common email deliverability problems, helping you get your messages where they belong—in front of your audience.

Understanding Email Deliverability vs. Delivery

Before diving into troubleshooting, let's clarify an important distinction:
Email delivery simply means your email was accepted by the recipient's mail server. However, this doesn't guarantee it reached the inbox.
Email deliverability refers to where your email lands after being accepted—ideally in the inbox, not the spam folder.
A high delivery rate might look good on paper, but if most of those emails end up in spam folders, your actual deliverability is poor. Success is measured by inbox placement rate (IPR), which tracks how many of your emails make it to the inbox.

Common Email Deliverability Problems

1. Authentication Issues

Email authentication proves you are who you claim to be. Without proper authentication, your emails are more likely to be flagged as suspicious.
Signs of authentication problems:
  • High bounce rates
  • Emails consistently landing in spam folders
  • Receiving authentication failure notifications

2. Poor Sender Reputation

Your sender reputation is like a credit score for email senders. Internet Service Providers (ISPs) use this to determine whether to deliver your emails to the inbox.
Signs of reputation issues:
  • Sudden drop in open rates
  • Increased spam complaints
  • Emails being blocked entirely by certain domains

3. List Hygiene Problems

Sending to inactive or incorrect email addresses damages your sender reputation over time.
Signs of list hygiene problems:
  • Increasing bounce rates
  • Hitting spam traps
  • Declining engagement metrics

4. Content Triggers

Certain words, phrases, or formatting choices can trigger spam filters.
Signs of content issues:
  • Similar content performs differently across segments
  • Emails containing specific topics always underperform
  • Preview tests show your email in spam folders

Troubleshooting Steps for Better Deliverability

Step 1: Verify Your Authentication

Proper authentication is your first defense against deliverability issues.
Action items:
  • Implement SPF (Sender Policy Framework) records
  • Set up DKIM (DomainKeys Identified Mail) authentication
  • Enable DMARC (Domain-based Message Authentication, Reporting & Conformance)
Most email service providers offer step-by-step guides for setting up these authentication methods. If you're unsure whether your authentication is working correctly, use tools like mail-tester.com to check.

Step 2: Monitor Your Sender Reputation

Your reputation follows your sending domain and IP address.
Action items:
  • Check your domain reputation using tools like Google Postmaster Tools
  • Monitor your IP reputation through services like Sender Score
  • Track spam complaint rates in your ESP analytics
If you discover reputation issues, gradually rebuild by sending only to your most engaged subscribers first, then slowly expand as metrics improve.

Step 3: Clean Your Email List

Regular list maintenance is crucial for deliverability health.
Action items:
  • Remove hard bounces immediately
  • Implement a sunset policy for unengaged subscribers
  • Use double opt-in for new subscribers
  • Never purchase email lists
Consider running a re-engagement campaign before removing inactive subscribers. This gives genuinely interested contacts a chance to stay on your list while helping you identify who should be removed.

Step 4: Optimize Your Content

Content that triggers spam filters can undermine all your other deliverability efforts.
Action items:
  • Avoid spam trigger words (like "free," "guarantee," or excessive punctuation)
  • Maintain a good text-to-image ratio
  • Test emails before sending to larger audiences
  • Create relevant, valuable content your subscribers want
Remember that engagement metrics like opens and clicks positively impact your deliverability, so focus on creating content your audience actually wants to receive.

Step 5: Implement Proper IP Warming

If you're sending from a new IP address, you need to establish trust gradually.
Action items:
  • Start with small volumes to your most engaged subscribers
  • Gradually increase sending volume over several weeks
  • Monitor metrics closely during the warming period
  • Maintain consistent sending patterns
Sudden spikes in sending volume from a new IP address raise red flags with ISPs, so patience during this process is essential.

Step 6: Set Up Proper Feedback Loops

Feedback loops alert you when subscribers mark your emails as spam.
Action items:
  • Register for feedback loops with major ISPs
  • Automatically remove subscribers who complain
  • Analyze patterns in complaints to identify problematic content or segments
This proactive approach helps prevent further damage to your sender reputation.

Monitoring Deliverability Performance

Ongoing monitoring is essential for maintaining good deliverability. Key metrics to track include:
  • Open rates: A sudden drop may indicate inbox placement issues
  • Bounce rates: Should remain below 1% for healthy deliverability
  • Spam complaint rates: Keep below 0.1% (preferably under 0.01%)
  • Unsubscribe rates: Should stay under 0.3% per campaign
Use these metrics as early warning signs of potential deliverability problems.

When to Consider Professional Help

Sometimes deliverability issues require specialized expertise. Consider working with a deliverability consultant if:
  • You've tried the steps above without improvement
  • You're experiencing a deliverability crisis affecting business results
  • You're planning a major change to your email program
  • You need to recover from a blocklisting

Final Thoughts

Email deliverability isn't a set-it-and-forget-it task—it requires ongoing attention and maintenance. By following these troubleshooting steps and best practices, you'll be well on your way to better inbox placement and more successful email campaigns.
Remember that deliverability is ultimately about trust. When you send relevant, wanted emails to people who have explicitly asked to hear from you, and you maintain proper technical standards, good deliverability naturally follows.
Start implementing these fixes today, and watch your email performance improve as more of your messages successfully reach your subscribers' inboxes.