An email spam checker is a tool that scans your email templates for deliverability issues. From spam trigger words and missing authentication records to image-heavy designs, these issues can cause your campaigns to land in spam instead of the inbox.

ConvertNow’s free spam checker is built for marketers, SaaS teams, and agencies who want higher deliverability without the guesswork.

How to Create Email Templates That Avoid Spam Filters

Nearly 49% of all emails sent globally are flagged as spam.

Poorly structured emails are more likely to be filtered out, making it harder to reach your audience.

This guide shows you how to use our Spam Checker to review your HTML email templates, identify spam triggers, and get actionable tips to improve deliverability.

1. Why Spam Filtering Still Matters in Email Marketing

Spam filtering still matters because it directly affects whether your emails reach the inbox or disappear into the spam folder.

Internet Service Providers (ISPs) like Gmail, Outlook, and Yahoo use advanced spam filters to protect users from unwanted or harmful messages.

These filters evaluate everything from your sender reputation to your email’s HTML structure before allowing it through.

For marketers, this means playing by strict rules.

Unlike one-on-one cold emails, marketing templates for campaigns or newsletters are sent to larger, permission-based lists.

That volume increases the chances of being flagged if your emails contain bad formatting, spammy language, or poor code.

Even beautifully designed HTML emails can trigger spam filters if the structure is messy or includes suspicious elements.

That’s why understanding and respecting spam filters is essential, not just for good deliverability, but for making sure your audience actually sees what you send, so let’s dive into how we can keep our emails out of the spam folder and right into the inbox.

2. Common Spam Trigger Words to Avoid

Spam trigger words are terms and phrases that email filters (e.g., Gmail, Outlook) flag as suspicious, often linked to unsolicited or overly promotional content.

These words, like “FREE MONEY NOW!!!” or “ACT FAST,” immediately signal potential spam to algorithms. Filters learn these patterns, directly impacting your sender reputation and whether your emails reach the inbox or spam folder.

To help you navigate this, here are key categories of spam trigger words you should be aware of:

• Financial & “Get Rich Quick”: Free, Cash, Money, Loan, Credit, Debt, Income, Investment, Opportunity, Make money, No strings attached, Work from home.
• Urgency & Scarcity: Act now, have limited time, be urgent, don’t miss out, have an exclusive offer, while supplies last, have a final chance, and are instant.
• Medical & Health: Cure, Miracle, Diet, Weight loss, X-rated, Viagra, Supplements, Lose weight.
• Marketing Buzzwords: Discount, Deal, Promotion, Offer, Guaranteed, Winner, Congratulations, Prize, You’ve been selected.
• Overly Aggressive Sales: Buy now, Order now, Call now, Click here, Big savings, Incredible deal.

When your email copy contains too many of these words, it significantly increases your “spam score” – an internal rating spam filters assign to your email.

The higher your spam score, the more likely your email will be filtered. 

Remember, the goal of your email copy is to be helpful and valuable, not to sound like a late-night infomercial. Instead of “Act now!“, consider “Ready to learn more?” or “Explore our latest collection.”

It’s about building trust, not creating artificial pressure.

I highly recommend checking out this comprehensive guide on Spam Words to Avoid.

3. Best Practices for Subject Lines and Body Copy

Your subject line is your email’s first impression, where many emails falter.

Spam filters are highly attuned to subject line patterns.

So, how do you stay persuasive without sounding like you’re trying to con someone?

Personalization is Powerful: 

Using your subscriber’s first name in the subject line (e.g., “John, exciting news for you!“) can significantly improve open rates and signal to filters that your email is relevant.

In fact, personalized subject lines can increase open rates by 26%, according to an extensive study by Campaign Monitor.

It shows you’ve done your homework and are speaking directly to them.

Clarity Over Clickbait: 

Be clear and concise about what’s inside. “Your July Newsletter” or “New Arrivals at [Your Brand]” are far more effective and trustworthy than “YOU WON!!!” or “Open ME for a surprise!“

A study by Return Path found that 69% of email recipients report email as spam solely based on the subject line. So, transparency is key.

Avoid ALL CAPS: 

THIS IS SCREAMING AND SPAM FILTERS HATE IT. Seriously.

It’s perceived as aggressive and unprofessional, and emails written in all caps are more likely to be flagged as spam or ignored by readers.

Instead, use sentence case or bold text to highlight key points without triggering filters.

For example, write Get 20% off your first order instead of GET 20% OFF YOUR FIRST ORDER!!!

Excessive Punctuation: 

Using too many exclamation marks (e.g., “Sale!!!“) or dollar signs (“$$$“) is another red flag.

Stick to one or two at most.

Over-punctuation makes your email look spammy and less trustworthy to both filters and readers.

No Clickbait Phrasing: 

Phrases like “You won’t believe what happened next!” might work for YouTube videos, but they reek of spam for emails. Your subscribers value their time, so give them a clear reason to open.

The same principles apply to your body copy.

Focus on providing value. Break up long paragraphs into shorter, digestible chunks.

Use bullet points and bold text to highlight key information. 

Also, always, consistently, deliver on the promise of your subject line.

These email writing tips for deliverability are about avoiding filters and creating a better experience for your readers.

4. The Text-to-Image Ratio Rule

The ideal text-to-image ratio is generally considered to be around 60% text to 40% images, or even better, a higher percentage of text.

If your email is 90% images and 10% text, you invite spam filters to flag you.

Why Image-Heavy Emails Trigger Spam Filters

Emails packed with images are a major red flag for spam filters because spammers often use them to hide malicious content.

This reliance on visuals prevents filters from reading your message, raising immediate suspicion.

• Lack of Scannable Content: If filters can’t extract meaningful text, they assume it’s obfuscated content, a common spam tactic.
• Increased File Size: Large images can slow down loading times, especially on mobile devices, leading to a poor user experience. ISPs prefer emails that load quickly.
• Accessibility Issues: Users with visual impairments who rely on screen readers won’t be able to access the content of an all-image email.

How to Optimize Images for Better Deliverability

To ensure your emails load quickly and avoid spam filters, proper image optimization is essential.

It helps your messages look great, reach the inbox, and provide a good experience for your subscribers.

Here’s how:

• Use Alt Text: Always include descriptive alt text for all your images. This serves two purposes: it provides context if the image doesn’t load and gives spam filters something to “read.”
• Compress Images: Before uploading, compress your images to reduce their file size without sacrificing quality. Tools like TinyPNG or Compressor.io are great for this.
• Don’t Use Images for Core Content: If crucial information is embedded in an image, you risk it being missed or filtered. Always have your main message in plain text.
• Balance Visuals with Text: Integrate your images naturally within your text, rather than having them dominate the layout.

5. Formatting Tips That Improve Deliverability

Beyond the words and images, the very structure of your email plays a critical role in deliverability.

Think of it as the foundation of your email house.

a). Clean HTML Structure 

Cluttered or poorly coded HTML is a major red flag.

It raises suspicion with spam filters, making them think you’re hiding content, and directly impacts how reliably your email renders across different clients, hurting user experience.

• Inline CSS: While external stylesheets are common for websites, inline CSS (styling directly within the HTML tags) is generally preferred for emails because not all email clients support external stylesheets.
• No Extra Tags or Bloat: Avoid unnecessary <div> tags, empty paragraphs, or extraneous code generated by some email builders. Keep it lean and clean.

b) Responsive Design Across Devices 

Litmus research indicates that 42% of email opens occur on mobile, responsive design is a necessity.

Emails that don’t display well on mobile can lead to frustrated users marking them as spam, negatively impacting your sender reputation. 

c) Include Unsubscribe Links and Physical Address 

This is a legal requirement and a trust signal. (e.g., CAN-SPAM Act in the US, GDPR in Europe).

A clear, easily accessible unsubscribe link is crucial.

Don’t hide it or make it difficult to find.

Similarly, including your physical address at the bottom of your email is a trust signal and a legal mandate.

It shows you’re a legitimate business.

d) Understanding Email Authentication: DKIM, SPF, and DMARC

DKIM, SPF, and DMARC are essential for email deliverability.

They prove to ISPs that your emails are authentic and haven’t been forged, helping you stay out of the spam folder.

• SPF (Sender Policy Framework): Authorizes which mail servers are permitted to send email on behalf of your domain.
• DKIM (DomainKeys Identified Mail): Provides a way to verify that the email was actually sent by the domain it claims to be from and hasn’t been tampered with.
• DMARC (Domain-based Message Authentication, Reporting & Conformance): Builds on SPF and DKIM, giving senders the ability to tell receiving mail servers what to do if an email fails SPF or DKIM checks (e.g., quarantine, reject). 

Setting up these authentication protocols properly tells ISPs that you are who you say you are, significantly reducing the likelihood of your emails being marked as spam.

If you’re unsure about these, contact your ESP’s support or your IT team for assistance.

These avoid spam filter best practices are non-negotiable for serious email marketers.

6. How Our Spam Checker Works

Even with all these best practices, it’s easy to miss something.

That’s where a good spam checker comes in handy.

Our free email template spam checker is designed to give you a quick, comprehensive audit of your email before you hit send.

Step 1: Paste your Email HTML

Begin by pasting the complete HTML code of your email into the editor to start the validation process.

After pasting your email HTML, click “Check Spam Score.” 100/100= the best score email will not be marked spam.

Step 2: Get Your Spam Analysis Results

Once your HTML is processed, you’ll immediately receive a detailed report outlining your email’s spam score and highlighting any detected issues.

What it checks: 

Our tool analyzes various elements within your email to identify potential spam triggers and deliverability issues.

Here’s a breakdown of what our checker scrutinizes

• Spam Words Detection: Scans your subject and body for spam trigger words, flagging problematic terms for rephrasing.
• HTML Structure: Scrutinizes your email’s code for messy tags or unclosed elements that can trigger spam filters.
• Unsubscribe Link: Verifies your unsubscribe link’s presence and correct format, which is essential for compliance and avoiding complaints.
• Text Content Ratio: Analyzes your text-to-image balance, assessing if the ratio is optimal or too image-heavy for deliverability.
• Image Content: Examines images for issues like hidden text or large file sizes, ensuring visuals don’t raise spam flags.

How to interpret your results:

After clicking ‘Check Spam Score,’ you’ll receive a detailed report to understand your email’s deliverability.

Your Overall Spam Score (e.g., 70/100, as seen in the example) reflects its general health; while 100/100 is the ideal for inbox placement, a score of 70/100 indicates issues that demand immediate attention to ensure your email reaches its recipients.

Review the Detailed Breakdown for each category (like “Spam Words Detection,” “HTML Structure,” etc.) to see specific findings and areas for improvement.

Pay close attention to “Problem” (red) and “Warning” (yellow) statuses, as these pinpoint crucial actions needed to boost your result.

Ready to see how your email measures up?

Don’t leave deliverability to chance! Test your email template with our free tool today!

7. Bonus: Tips to Improve Inbox Placement

Beyond avoiding spam triggers, there are proactive steps you can take to build a stellar sender reputation, which directly impacts inbox placement.

• Engagement Signals (Open/Click Rates): This is paramount. ISPs monitor how their users interact with your emails. If any of your subscribers are opening your emails, clicking on your links, and replying, it tells the ISPs, “Hey, this sender is sending valuable content!” Focus on creating compelling content that your audience wants to engage with. A high engagement rate is the ultimate signal of a legitimate and welcome sender.
• Warming Up Your Sending Domain: If you’re new to email marketing or have a new sending domain, you can’t just send thousands of emails. ISPs are suspicious of sudden, large spikes in email volume from unknown domains. “Warming up” means gradually increasing your sending volume over several weeks or months. Start with your most engaged subscribers, send small batches, and slowly ramp up. This builds trust with ISPs over time.
• Using a Dedicated Sending IP vs. Shared:
  • Shared IP: Many smaller businesses and new senders start on shared IPs, where your emails are sent from the same IP address as other senders. The pro is that the deliverability reputation is shared, but the con is that if another sender on that shared IP misbehaves (sends spam, gets blacklisted), your deliverability can suffer too, even if you’re doing everything right.
  • Dedicated IP: A dedicated IP address is exclusively yours. This means your sender’s reputation is entirely in your hands. The benefit is full control, but the responsibility is also yours to maintain a good sending reputation. This is typically recommended for senders with high email volumes (e.g., over 100,000 emails per month) who can consistently send high-quality, engaging content.

Wrapping Up

By focusing on these proactive strategies and diligently avoiding spam triggers and optimizing your email templates, you’re not just avoiding the spam folder, you’re building a strong, trusted relationship with both ISPs and, most importantly, your subscribers.

Happy emailing!