Why Too Many Links Cause Emails to Be Marked as Spam?

Last month, our organization sent out one of its feature launch emails to 50,000 people. 

After all the prep work and a great offer, only 12% of recipients actually saw the email. 

Why? 

Five harmless-looking links were enough to trigger spam filters and push their emails to the spam folder instead of the primary inbox of their email list.

And It’s a very common email mistake. 

They spend hours crafting the perfect subject line, designing the layout, and adding helpful links only to have their emails land in spam. 

What they don’t realize is that adding too many links (like to social media, blog posts, or product pages) can seriously hurt deliverability.

According to Validity’s 2025 Email Deliverability Report, 22% of legit emails still end up in spam and too many links is the third biggest reason why. 

For a team sending 10,000 emails a month, fixing this one issue could boost responses from 46 to 119. 

That’s a 159% jump in the performance of the email campaigns! 

Let’s break down why your links could be tanking your emails and how to fix it fast.

How do spam filters actually evaluate your emails?

Email providers like Gmail, Outlook, and Yahoo don’t just randomly decide which emails go to spam. 

They use AI-based algorithms that constantly analyze dozens of factors in real-time, with links playing a much bigger role than most people understand.

Source

Every email gets assigned a spam score based on various elements. 

Think of it like a point system where certain characteristics add points, and once you hit a threshold, your email gets flagged as spam.

Modern email-based spam detection examines:

• Link quantity and destination quality
• Text-to-link ratios and content balance
• Sender authentication and domain reputation
• Recipient engagement patterns and behavior
• HTML structure and coding quality

Modern spam filters also apply machine learning, which means they’re constantly getting smarter. 

They analyze patterns from millions of emails to identify what “spammy” behavior looks like. 

If your email matches patterns that typically come from spam, you’ll get flagged regardless of your good intentions.

Email service providers usually focus on three key metrics:

• Spam scores: The technical evaluation of your email content
• Sender reputation: Your historical performance across all campaigns
• User engagement: How recipients typically interact with your emails

When you understand that spam filters are designed to protect users from overwhelming or deceptive content, it becomes clear why multiple links raise red flags. 

Why links in emails trigger spam detection?

Spam filters are built to protect users from scams, especially phishing attacks. 

One of the strongest red flags? 

Too many links. 

Emails packed with multiple links especially to different domains often mimic the exact patterns used by malicious senders.

Let’s break down what spam filters are really looking at.

#1 Too many domains = Major suspicion

If your email links out to your website, a YouTube video, a Google Drive file, your LinkedIn profile, and a third-party article that’s five different domains. 

Spam filters see that and immediately get suspicious. 

That’s a classic phishing move: mix legit and shady links to trick people.

“Even one poorly chosen link can spoil an otherwise excellent email campaign. 

Strategic link management isn’t optional anymore, it’s fundamental to email success.”

— Chad White, Head of Research, Oracle Marketing Cloud

#2 Sketchy link destinations

Even one link to a low-reputation or unfamiliar site can get you flagged. 

Think:

• New or recently registered domains
  
• Sites without HTTPS (SSL certificate)
  
• Pages associated with spam or malware in the past

Spam filters evaluate not just how many links you include, but also where they point.

#3 Bad link-to-text ratio

Short email, lots of links? 

That’s a red flag. Spam filters calculate how much of your email is links vs. actual content. 

If there’s too little text and too many links, your message looks automated and low quality.

What does the data show?

• 2–3 links to trusted domains = Best inbox placement
  
• 5+ links = 45% higher chance of landing in spam
  
• Cold emails with 3+ links = 60% fewer replies than those with just 1 focused CTA
  
• Unverified domains = Risky even if it’s the only link

#4 People notice too

It’s not just the algorithms. 

When recipients see an email cluttered with links, they often feel overwhelmed or worse, think it’s a scam. 

That means less engagement, more spam reports, and a declining sender reputation over time.

How can I use the right number of links to avoid spam filters?

The ideal number of links depends on the type of email, but less is almost always more.

A) For cold outreach

Stick to 1–2 links max, usually a primary CTA (like a calendar link) and maybe one supporting link (like a case study). 

More than that starts looking like mass marketing.

Generally, for cold email campaign, it’s recommended to distribute the total number attached links over multiple email follow-ups.

This way you can keep 1-2 links max for each sequence without getting flagged.

B) For newsletters & information 

You can include 2–4 links, but only if your email has enough content to support them (e.g., 800+ words). 

Short emails with too many links often trigger spam filters.

What the data says?

As per our recent internal survey, we found out that -: 

• 1–2 links: 85% inbox placement
  
• 3–4 links: 67%
  
• 5+ links: 43%

Read more about How Links Impact Cold Email Deliverability?

Technical factors that make link problems worse

Even if you limit your links, certain technical issues can still send your emails to spam. 

Here’s what to watch out for:

#1 Raw URLs look spammy

Bad: https://www.example.com/long-page-url ❌

Good: “View our pricing options” (as hyperlinked text) ✅

Spam filters prefer links embedded in natural, descriptive anchor text.

#2 URL shorteners raise red flags

• Tools like bit.ly or tinyurl hide the final destination
  
• Spam filters treat them as suspicious (common in phishing emails)

✅ Use branded shorteners like links.yourcompany.com for better trust.

#3 Bad domain reputation hurts you

One sketchy link can tank your whole email. 

Watch out for:

• Newly registered domains
  
• Missing SSL (no HTTPS)
  
• Spammy or blacklisted sites
  
• Domains with high bounce rates

✅ Use tools like Whois lookup to check domain trustworthiness.

#4 Messy HTML = Spam trigger

Poorly coded emails make spam filters nervous.

✅ Use clean HTML with proper nesting, image alt text, and heading structure.

❌ Don’t hide links in tiny fonts or match them to background color.

#5 No email authentication? Big problem.

Without SPF, DKIM, and DMARC setup, your links (and entire email) get extra scrutiny.

✅ These protocols prove you’re a legit sender. Don’t skip them.

6 Email smart link strategies to stay out of spam

Want your emails to hit inboxes not spam folders? 

These link tactics work across industries and campaign types.

#1 Stick to one clear CTA

• Focus your email around one main action (e.g., “Book a demo”)
  
• Support it with one relevant link (e.g., a case study)
  
• ❌ Avoid stuffing in blog, social, pricing, and company links all at once

#2 Link to your own domain first

• Prioritize links that point to your website
  
• If linking externally, choose reputable sources only

Pro tip: Create a single “Resources” page on your site instead of linking to 5+ external pages

#3 Place links strategically

• Put your primary CTA link above the fold
  
• Avoid placing multiple links in one paragraph
  
• Space links out naturally and surrounds them with supporting text

#4 Use descriptive anchor text

• “View pricing details”
• “Download the ROI calculator”
• “See customer success stories”
• “Click here” or “Learn more”

This helps both users and spam filters trust your links.

#5 Be cautious with external links

• Limit to one external link per email
  
• Always double-check the domain’s reputation
  
• For multiple third-party resources, link to a curated page on your site

How SmartReach.io help you stay out of spam?

SmartReach.io is a cold email software with an aim of improving your email deliverability. 

SmartReach.io’s email deliverability suite helps you land in the inbox, not spam. 

With WarmupHero, your sending volume increases gradually while boosting opens and replies, building a strong sender reputation. 

The inbox rotation feature spreads emails across multiple verified inboxes to avoid spam filters flagging high-volume sends. Plus, ESP matching ensures your emails align with the recipient’s email provider, creating patterns that filters trust.

SmartReach also keeps your sender reputation safe with email verification that checks DNS, SMTP, and MX records and revalidates through third-party checks for 80%+ accuracy, so you only send to valid addresses. 

Spam testing scans your setup before sending, checking authentication, broken links, unsafe HTML, and blacklists. 

Global blacklist monitoring alerts you if your domain or account gets listed and pauses sending automatically to protect your campaigns.

Try SmartReach free for 14 days today

Best practices for including links in the email (by industry)

Not all emails and not all industries can follow the same rules when it comes to links. 

Here’s how to customise your link strategy based on email type and audience expectations:

B2B Cold Outreach → Keep It Minimal

• Ideal link count: 1
  
• Focus on starting a conversation, not showcasing everything
  
• Best-performing emails typically link to a scheduling page or relevant resource

E-commerce & Retail → Feature, Don’t Flood

• Ideal link count: 3–4 max
  
• Highlight a few top products + 1 link to the full collection
  
• Ensure product links are tightly related and supported by descriptive content

🛑 Avoid overwhelming users with 10+ product links, this kills deliverability.

Newsletters & Content Marketing → Curate Wisely

• Highlight your 2–3 best pieces of content
  
• Add one link to a “More resources” or blog hub
  
• Digest-style formats work best: fewer links, more context
  

Pro tip: Use a “featured article” approach to drive focus and engagement.

Educational Content → Prioritize Value

• Link to 1 high-impact resource (e.g., whitepaper, featured blog)
  
• Optionally include a link to your content library
  
• Make sure the value is crystal clear in your anchor text
  

Transactional Emails → Function First

• These can include multiple links:
  
  • Track order
    
  • View invoice
    
  • Contact support
    
• Spam filters allow more flexibility but don’t mix in promotions

Promo-heavy transactional emails often get flagged or annoy users. Keep them clean and focused.

Other factors that work together with link issues

While links play a major role in email deliverability, they don’t act alone. Several other factors can either amplify or minimize link-related issues. 

Email authentication is foundational without SPF, DKIM, and DMARC in place; even a well-crafted email with just one or two links can land in spam. 

These protocols prove you’re a legitimate sender.

Content balance also matters. 

Emails that are mostly images with minimal text make your links stand out more and not in a good way. 

Aim for at least 100–150 words of content for every link to maintain a healthy ratio.

Your sender reputation is equally important. If your domain has a history of low engagement or spam complaints, it’ll take more than a good link strategy to fix your inbox placement. 

Keep your email lists clean, manage unsubscribes promptly, and send only to engaged audiences.

Even your email subject line and sender name can impact how filters treat your links. 

Spammy or clickbait-style subject lines raise red flags, so stay clear, relevant, and authentic.

To simplify all of this, tools like SmartReach.io offer built-in spam checks, email sequence generation, etc. all designed to help you hit the inbox. 

Try SmartReach free for 14 days today and take the guesswork out of email deliverability.

Frequently asked questions about email links and spam

How many links can I include before triggering spam filters?

Most email providers flag emails with more than 5 links as potentially suspicious. For ideal deliverability, stick to 2-3 links for newsletters and 1-2 for cold outreach.

Do shortened URLs trigger spam filters?

Yes, URL shorteners like bit.ly can trigger spam filters because they hide the destination. Apply branded shorteners or descriptive anchor text instead.

What link-to-text ratio prevents spam?

Maintain at least 100-150 words of content for every link included. This 75:1 ratio signals value over promotion to spam filters.

Can one bad link ruin my entire email?

Yes, even one link to a domain with poor reputation can trigger spam filters for your entire email. Always verify external link destinations before including them.

How do I know if my links are causing spam issues?

Monitor your email analytics for declining open rates, increasing spam complaints, and lower inbox placement rates. Tools like Google Postmaster or MailGenius can help identify specific issues.

What’s the difference between internal and external links for spam filters?

Internal links (to your own domain) are generally safer and less likely to trigger spam filters. External links are scrutinized more carefully, especially if they point to unknown or low-reputation domains.