How to Find + Troubleshoot Email Deliverability Issues

Every cold emailer faces some sort of email deliverability issues at some point in their outreach campaigns. 

No matter how top-notch your email infrastructure is or how good of a sender you’re, cold email campaigns will occasionally meet different types of email deliverability problems.

Now, these deliverability issues can kill your campaign by sending your emails to SPAM instead of the primary inbox of the prospects.

So, understanding and addressing these email deliverability issues is key to optimize your cold email campaigns for better performance and achieve a higher ROI.

In this article, we’ll find out ⤵ 

• Different ways of finding crucial email deliverability issues
• Best ways to solve those deliverability issues and

So, let’s get started with the basics. 

What is email deliverability?

Email deliverability refers to the ability of an email to successfully reach the intended recipient’s inbox (usually, the primary email inbox).

It consists of multiple factors like –

• sender reputation, 
• email authentication and 
• the content of the email itself.

Email deliverability issues arise when your emails either land in the spam folder of the recipients or they’re blocked from the recipient’s server altogether.

There are multiple reasons behind these email deliverability problems which we’ll cover later in this article.

‘Email Delivery’ issues v/s. ‘Email Deliverability’ issues

Although people search these terms interchangeably on the internet looking for answers, they have distinct meanings – 

• Email delivery issues → Occur when an email fails to reach the recipient’s server. Common reasons include incorrect email addresses, server downtime, or recipient inboxes being full.

For example, a “hard bounce” indicates a permanent delivery issue, while a “soft bounce” may be temporary.

• Email deliverability issues → These happen when an email reaches the recipient’s server but fails to land in their inbox, often ending up in the spam or promotions folder. Factors like sender reputation, spam filters, and email content play a significant role.

For running a smooth and optimized cold email campaign, you need to understand + resolve both types of issues to reach your prospects.

Why are email deliverability rules getting stricter?

The volume of spam emails has grown significantly, leading mailbox providers like Google and Yahoo to enforce stricter rules. 

According to a study by Statista, around 347 billion emails are sent daily, and nearly half are classified as spam. 

Email service providers such as Gmail and Outlook continuously implement tighter controls to safeguard inboxes from unwanted and malicious messages.

Al Iverson, one of the most prominent email industry researchers and experts from Valimail, explains-

“Providers are under pressure to reduce spam. Stricter rules help ensure that legitimate senders stand out while spam and phishing attempts are minimized.” 

These tighter rules mean senders must maintain high standards for authentication, engagement, and content quality of their cold emails.

How to find email deliverability issues?

Diagnosing email deliverability problems is the first step to troubleshooting these issues.

Here’s how to find out the email deliverability problems –

1. Monitor email bounce rate

When you see email bounce rate numbers are increasing rapidly, it may indicate your campaign is going through email deliverability issues.

A high email bounce rate will cause lost opportunities.

A standard email bounce rate is upto 3%.

If your email copies contain certain spam-triggering keywords like “free”, “guaranteed”, “100%” etc., it will be caught by spam filters set-up by the email services. (There are more than 70+ such keywords, check out the list)

Check for the 2 types of email bounces – 

• Hard Bounces → Permanent issues caused by invalid email addresses or blocked domains. 

For example, sending emails to nonexistent domains like [email protected] will result in hard bounces.

• Soft Bounces → Temporary issues like a full inbox or server problems. Monitor these to identify patterns and act accordingly.

Check inside your email outreach software for these issues. 

Some tools like SmartReach.io provides real time update on email bounces. You may check this out too.

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2. Check email spam complaints

High spam complaints damage your sender reputation. 

If your emails are marked continuously as spam by the recipients, your campaign’s deliverability will drop.

It may be due to wrong messaging or targeting the wrong ICP that the recipients find irrelevant.

Aim to keep the spam complaints below 2%.

You will find the spam rate inside any email marketing software you use. 

Cheat Sheet → How to Avoid Cold Emails Going To Spam

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3. Analyze email content

Run your email copies through tools like Mail Tester to identify potential spam triggers. 

Check for email content issues like –

• Overly promotional language in the copy ❌
• Broken links ❌
• Missing unsubscribe options ❌
• High text to HTML ration in the email copy ❌
• Spam-triggering keywords ❌
• Using all CAPS in the email subject line etc ❌
• Incorrect hyperlinks ❌

These issues kill your sender score (a numerical rating from 0 to 100 that evaluates an email sender’s IP address reputation).

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4. Check for blacklisted domains or IP addresses

Check if the domain you use for the cold email set-up has been blacklisted by the email services or not.

Sometimes due to poor sender reputation or for high amount of spam complaints, domains attached to email accounts are blacklisted.

When this happens, email services such as Gmail, Yahoo, Outlook etc. view your emails as spammy and unhelpful and push your emails to the spam instead of the primary inbox of the recipients.

Use free tools like MXToolbox to monitior domain or IP blacklist status and SPF/DKIM configurations.

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5. Review email authentication set-up

Verify SPF, DKIM, and DMARC records to ensure proper email authentication. 

For example, an incorrect SPF setup could cause emails to fail validation and your emails start never land in the primary inbox.

Use a free tool like Glockapps to check the email authentication.

You can use the below tutorial to set-up the authentication.

Guide: Steps to authenticate SPF, DKIM, and DMARC for Google Workspace

8 Ways to troubleshoot email deliverability issues

Before you start this section, you may want to read How to Improve Email Deliverability for different hacks to improve deliverability.

In this section, we’ll focus on quick and actionable strategies to fix email deliverability problems.

#1. Verify your email authentication protocols

Email authentication is the first step to establishing trust with email services and preventing your messages from being flagged.

• SPF (Sender Policy Framework): Verify your SPF records to authorize specific servers to send emails on your behalf. Use tools like MXToolbox for quick checks.

• DKIM (DomainKeys Identified Mail): Ensure DKIM is configured to authenticate your email content. Misalignment can lead to emails being rejected.

• DMARC (Domain-Based Message Authentication): Set up DMARC policies to block unauthorized emails and prevent domain spoofing. 

💡Extra hack: Implement BIMI (Brand Indicators for Message Identification) to display your logo in email inboxes, improving trustworthiness

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#2. Monitor bounce rates regularly

High bounce rates indicate problems with your email list or sending practices.  

• Hard Bounces: Remove invalid or non-existent addresses immediately.  
• Soft Bounces: Monitor and retry sending emails after a brief interval.  

📌 Practical Tip: Use any email verification tool to clean your email lists regularly before pushing them into campaigns.  

You can use the free email validation system inside SmartReach.io that provides unlimited email validation.

It alerts you with delivery status of the email list before you push the email lists into campaign for email sending.

This is a way step to avoid deliverability problems and reduce bounce rates significantly.

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#3. Maintain a clean and segmented email list

A well-maintained email list ensures better engagement and reduces the risk of deliverability issues.  Here’s what to do:

• Clean inactive contacts → Remove prospects who haven’t engaged in the last six months.  

• Use double opt-in → Require recipients to confirm their email addresses to ensure the list is clean from the start.  

• Segment based on engagement → Group users into active, moderately active, and dormant segments to send personalized campaigns.  

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#4. Optimize email content for deliverability

 The way your email is written and structured can significantly impact deliverability.  

• Avoid spam-trigger words like “Act Now,” “Free,” “Limited Offer” etc. that can trip spam filters.  
• Personalize email content that is relatable and helpful to the recipients.
• Keep HTML content inside the email copy clean.
• Avoid excessive images or poorly written HTML code, as they can trigger spam filters.  

💡 Quick hack: Use email testing tools like Mail Tester or GlockApps to ensure your email is spam-free and inbox-ready.  

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#5. Warm-up new IP addresses and domains

 If you’re using a new domain for cold emailing, gradually build your sending reputation.  

• Start small → Send emails to a small, highly engaged segment of your list.  
• Increase gradually → Scale up email volume week by week to avoid spam triggers.  
• Track engagement → Monitor open and click rates to gauge deliverability.  

💡 Pro tip: Use email warm-up tools like WarmupHero to automate this process effectively.  

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#6. Check for blacklist issues 

If your domain or IP is blacklisted, email providers may block your messages entirely.  

• Regularly monitor blacklist status of your IPs. Use tools like MXToolbox or MultiRBL to check if you’re listed.  

• Remove yourself from blacklists. Contact the blacklist provider and resolve the issue by improving your practices.   

SmartReach.io monitors your domain and IP against 50+ global blacklists, ensuring real-time alerts if your domains are blacklisted. 

This proactive monitoring prevents email deliverability issues by letting you act quickly to maintain your sender reputation.

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#7. Increase the email engagement

  Improving engagement signals to email providers that your messages are valuable and not spam.  

• Improve the email responses from your cold email campaigns to improve the email deliverability.
• Ask recipients to add your email address to their contacts to bypass filters.  

Suggested → Reply Rate Cheat Sheet

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#8 Use analytics to pinpoint issues inside campaigns

 Analytics tools can reveal where your deliverability problems lie inside your email campaigns.

Use cold email software like SmartReach.io that provides detailed analytics and reports for a campaign and prospect level breakdown.

Once you find out the issues inside campaign, you can use multiple hacks to improve those metrics and improve deliverability.

By combining these advanced hacks with consistent monitoring and optimization, you’ll resolve email deliverability issues effectively and ensure your campaigns achieve their full potential.

Bottom line

Email deliverability requires constant monitoring and maintenance to ensure your messages consistently land in the primary inbox of the recipients. 

SmartReach.io simplifies this process with its premium deliverability features.

From unlimited email address validation and engagement tracking to real-time bounce analysis and domain authentication monitoring, SmartReach.io handles the technical aspects of email deliverability so you can focus on creating engaging campaigns. 

The platform’s built-in warmup feature and deliverability features help maintain optimal inbox placement rates while preventing potential issues before they impact your email performance.

Try SmartReach.io for free for 14-Days. (No credit card required)

Email deliverability issues: F.A.Qs

Q. What are the most common causes of email deliverability issues?

• Sending to unverified email addresses
• Poor domain or IP reputation
• Low email engagement 
• Failing to comply with GDPR or CAN-SPAM regulations

Q. How often should I validate my email list?

Validate your email list at least every 2 weeks to maintain high deliverability rates and reduce bounces.

Q. Can using purchased email lists hurt my deliverability?

Yes. Purchased lists often contain invalid or unengaged email addresses, leading to high bounce rates and spam complaints. Always use permission-based lists.

Q. What tools are best for improving email deliverability?

• Mail Tester: Tests emails for spam triggers.
• GlockApps: Monitors inbox placement.
• MXToolbox: Checks blacklist status.
• ZeroBounce: Validates email addresses.
• SmartReach: Sends emails in the primary inbox of the recipients

Q. How do i fix email deliverability issues?

Fix email deliverability issues by authenticating domains with SPF, DKIM, and DMARC, removing invalid addresses, and monitoring bounce rates. Use reputable email providers, avoid spam triggers, and regularly clean email lists.

Q. What affects email deliverability?

Email deliverability is affected by – 

• Poor sender reputation, 
• SPF, DKIM, DMARC error, 
• Poor email list quality, 
• Spammy email content, 
• High bounce rates, and 
• Too many spam complaints

Q. How to improve email deliverability?

Improve email deliverability by using authenticated domains (SPF, DKIM, DMARC), avoiding spammy keywords, maintaining clean lists, and monitoring sender reputation.