Plain Text vs HTML Email for Cold Outreach: Which Performs Better?

Plain text emails consistently outperform HTML in cold outreach. The data shows 15-25% more replies. Here is why and the one exception.

Plain Text Wins. Every Time.

I have tested this across dozens of campaigns and hundreds of thousands of emails. Plain text cold emails get 15-25% more replies than HTML emails. This is not a marginal difference. It is the gap between a campaign that books meetings and one that dies in the spam folder.

The reason is straightforward. HTML emails contain code that spam filters can read but humans cannot see. Tracking pixels, hidden divs, embedded styles, image references, link wrappers. Every piece of HTML gives spam filters more signals to evaluate, and most of those signals point toward "this is marketing email, not a person writing to another person."

Why HTML Hurts Cold Email Deliverability

Tracking pixels. HTML emails almost always include a tiny invisible image that loads when the recipient opens the email. This is how platforms measure open rates. But email providers, especially Google, flag these pixels as a spam signal. They know that real person-to-person emails do not contain tracking pixels. Only mass email does.

HTML weight. A plain text email is a few kilobytes. An HTML email with styling, images, and tracking code can be 20-50KB or more. Email providers compare the ratio of visible text to hidden code. When the code outweighs the content, it looks like a marketing blast.

Rendering inconsistencies. HTML emails look different across email clients. What looks polished in Gmail might break in Outlook. A broken layout screams "mass email" and kills credibility. Plain text looks the same everywhere.

Link tracking wrappers. HTML emails often wrap every link in a tracking redirect. Instead of linking to yoursite.com, the email links to tracking.platform.com/redirect/abc123 which then redirects to your site. Spam filters flag these redirect URLs because they are commonly used in phishing attacks.

The Numbers

Across my client campaigns in 2025 and 2026, here is what I have seen consistently:

• Plain text cold emails: 3.5-5% average reply rate
• HTML cold emails (with images, buttons, styling): 2-3.5% average reply rate
• HTML cold emails with tracking pixels: 1.5-2.5% average reply rate

That 15-25% gap in reply rate translates directly to meetings. At 500 emails per day, the difference between a 3.5% and a 4.5% reply rate is 5 extra replies per day. Over a month, that is 100+ additional replies and roughly 50 more meetings. From the same list, same targeting, same offer. Just a different email format.

The One Exception

If your product is visual, a design agency showing portfolio work, an e-commerce brand, a product with a UI that sells itself, there is an argument for including one image in a follow-up email. Not the first email. Never the first email. But in email 3 or 4 of your sequence, after you have established some trust with the email provider, a single well-placed image can sometimes boost engagement.

Even in this case, keep the HTML minimal. One image, no tracking pixel, no styled template. Just plain text with an embedded image. And test it against a pure plain text version. Most of the time, plain text still wins even for visual products.

What to Do

Send plain text cold emails. No HTML templates. No images. No tracking pixels. No fancy formatting. Write your email like you are writing to one person from your personal inbox. Because that is exactly what cold email is supposed to look like.

Disable open tracking in your sending platform. Track replies instead. Reply rate is the only metric that matters for cold email, and it does not require any tracking code.