You've crafted the perfect cold email campaign to connect with potential clients. But instead of landing in their inbox, your carefully written messages are disappearing into the spam folder abyss. With the average cold email open rate hovering around just 44%, understanding what triggers spam filters is crucial for your outreach success.

Why Your Cold Emails Are Getting Flagged as Spam

Cold emailing remains a powerful outreach strategy, but the landscape is increasingly complex. Email service providers have become sophisticated in filtering out unwanted messages, and seemingly innocent practices can trigger these filters.

The CC Trap: A Major Deliverability Killer

One of the most overlooked spam triggers is the simple act of adding recipients to the CC field. While it might seem like an efficient way to loop in multiple contacts, this practice can significantly harm your deliverability.

"Thoughts on deliverability and whether adding a 'cc' to mostly cold email campaign will trigger spam?" asked one concerned marketer on Reddit. The consensus among email experts is clear: CC usage in cold emails raises red flags for spam filters.

Why? CC'ing multiple recipients:

• Signals mass emailing behavior (a classic spam characteristic)

• Reduces personalization

• Makes recipients feel like they're receiving a generic message

• Can expose email addresses to strangers (a privacy concern)

If you're considering "looping in a partner" on cold emails by adding them to CC, proceed with extreme caution. As one Reddit user advised: "Maybe you can do a test for 1 batch and see how it goes." This measured approach allows you to assess the impact on deliverability before risking your entire campaign.

Beyond CC: Other Common Spam Triggers

While CC usage deserves special attention, it's just one of many factors that can send your emails to spam purgatory:

1. Suspect Language and Phrases Certain words and phrases instantly trigger spam filters. These typically include:

   • "Get rich quick" terminology

   • Excessive use of "free," "guarantee," or "instant"

   • ALL CAPS or excessive exclamation marks!!!

   • Phrases like "no obligation" or "no purchase necessary"

   As one Reddit user noted: "Most of the spam emails I get are usually consistent 'get rich quick things' or if you use so many words that sound scammy, like free money, get rich fast."

2. Poor Email Authentication Proper domain authentication through SPF, DKIM, and DMARC records is essential. Without these technical safeguards in place, your emails are more likely to be flagged.

   "Did you authenticate your domain (SPF, DKIM, and DMARC)?" is often the first troubleshooting question when deliverability issues arise.

3. Lack of Domain Warming Sending high volumes of emails from a new domain without proper warming can trigger spam alerts.

   "When you buy new domains and email accounts, make sure to set up all the records properly and warm up for at least 14 days to build some credibility for your accounts," advises an experienced cold emailer on Reddit.

4. HTML-Heavy Content Excessive HTML, tracking pixels, and certain types of links can all contribute to spam filtering.

   "It's a type of link as well which can trigger spam filters. Basically, the goal is to keep your email 100% HTML free," notes one Reddit user discussing email tracking technology.

5. Generic Opening Lines Starting your email with phrases like "I came across your website" can immediately trigger deletion.

   "I never read further than 'I came across your website' before deleting something as spam," admits one recipient of cold emails.

Actionable Strategies to Avoid Spam Filters

Now that you understand what triggers spam filters, let's explore practical ways to improve your cold email deliverability:

1. Send Personalized, Individual Emails

Instead of using CC, send individual, personalized messages. This approach may require more time, but the improved deliverability is worth the effort.

If you need to involve multiple recipients, consider:

• Sending separate, personalized emails to each person

• Using a proper email marketing platform with BCC functionality

• Implementing a sequential follow-up strategy rather than including everyone at once

Tools like Kondo can help organize and track these conversations, especially when managing multiple leads. Kondo's labeling system allows you to categorize conversations (e.g., "Hot Lead," "Client," "Candidate") and set reminders for follow-ups, ensuring no important conversation gets lost.

2. Warm Up New Email Domains Gradually

When using a new domain for cold outreach:

• Start with low volumes (5-10 emails daily)

• Gradually increase sending over 2-4 weeks

• Engage in genuine two-way communications

• Ensure recipients open, reply, and mark your emails as important

3. Keep Content Clean and Relevant

To maximize deliverability:

• Avoid spam trigger words and phrases

• Keep emails concise (100-150 words is ideal)

• Use plain-text formatting when possible

• Include a clear, low-commitment call to action

• Minimize links (one or two at most)

4. Implement Proper Authentication

Set up these critical authentication protocols:

• SPF (Sender Policy Framework) records

• DKIM (DomainKeys Identified Mail) signing

• DMARC (Domain-based Message Authentication) policies

These technical measures signal to email providers that you're a legitimate sender, not a spammer using a look-a-like domain.

5. Clean Your Email Lists Regularly

Sending to inactive or incorrect email addresses increases bounce rates, which damages your sender reputation. Regularly:

• Verify email addresses before sending

• Remove hard bounces immediately

• Monitor engagement and clean inactive contacts

6. Test Before Full Deployment

Before launching a full-scale cold email campaign:

• Send test emails to seed accounts at different providers

• Use spam testing tools to identify potential triggers

• Run small-batch tests to assess deliverability

"Check deliverability of your emails weekly or at least every 2 weeks at the minimum," recommends one email marketing expert on Reddit.

Why Personalization Is Your Best Defense Against Spam Filters

Beyond technical considerations, the most effective way to avoid spam filters is creating genuinely valuable, personalized content that recipients want to engage with.

"Most people hate receiving marketing emails but are happy to be reached out to for advice, information, or a no-pressure video call," notes one Reddit user. This insight highlights the importance of offering value rather than immediately pushing for a sale.

Many users express frustration with receiving "dozens of templated cold emails stacking up daily, barely getting opened." To stand out:

• Research your recipients thoroughly before reaching out

• Reference specific details about their work or company

• Focus on solving their problems rather than promoting your solution

• Keep your message conversational and authentic

One effective approach is to set up a drip sequence that gradually builds relationship rather than overwhelming recipients with information in a single email.

When LinkedIn Is a Better Alternative

With cold email deliverability challenges mounting, some marketers are shifting to LinkedIn for direct outreach. LinkedIn messaging provides a professional context for connection without the same spam filter hurdles.

For LinkedIn outreach management, tools like Kondo can significantly enhance productivity. Kondo transforms LinkedIn's cluttered messaging system into a streamlined communication hub with features like keyboard shortcuts, snippets for frequently used messages, and reminder functionality to ensure timely follow-ups.

Conclusion: Finding the Balance

While spam filters present challenges for cold emailers, understanding and avoiding common triggers—especially risky practices like using CC fields—can dramatically improve your deliverability.

The most successful cold email campaigns balance technical optimization with genuine personalization. By focusing on creating value for your recipients rather than simply pushing your agenda, you'll not only bypass spam filters but also achieve the engagement and response rates that drive real business results.

Remember to regularly monitor your deliverability, test your approaches, and adjust your strategy based on results. With thoughtful implementation of these best practices, cold email can remain an effective channel in your outreach toolkit, even in today's challenging deliverability landscape.