You're about to hit send on your cold email campaign and you're stuck on one decision: should you send plain text or dress it up with HTML formatting?

This shouldn't be a hard choice, but it is - because the internet is full of contradictory advice. One blog says HTML looks more professional. Another says plain text gets better deliverability. Someone else claims plain text feels more personal.

Here's what actually happens when you test both at scale: plain text wins on reply rate almost every time. Not by a tiny margin. By a real one.

The Numbers: What We Actually See

From our data running hundreds of campaigns across service businesses and agencies, plain text emails average a 4-8% reply rate on cold outreach. HTML emails average 2-4%.

That's not a coincidence. That's pattern.

The reason is simple: plain text looks like it came from a real person who sat down and typed. HTML looks like a template. Even if your HTML email is beautiful and branded, it signals "this is a mass campaign" the moment it hits the inbox. The recipient's brain recognizes it before they consciously do.

Plain text doesn't have that signal. It looks like an email from a colleague who wants to talk about something specific.

Why Plain Text Actually Wins

It doesn't trigger spam filters as easily

This is the technical side. Email filters look at HTML code as a potential vector for phishing and malware. A lot of bad actors hide malicious code in HTML formatting. Plain text has no code to hide in. Email servers and spam filters treat plain text emails with less suspicion from the jump.

When you're trying to nail cold email deliverability, every little advantage counts. Plain text removes one variable.

It creates a lower barrier to response

When someone opens an HTML email, they're seeing something professionally formatted. That creates a psychological expectation: "this is a pitch, and I should probably think carefully about whether I care."

Plain text emails feel conversational. They lower the perceived formality. Your prospect is more likely to fire back a quick reply without overthinking it.

It's actually harder to screw up

HTML rendering is inconsistent across email clients. An email that looks perfect in Gmail might render weirdly in Outlook. Images might not load. Buttons might break. Plain text always looks the same everywhere.

When your email looks broken, you look broken.

When You Might Actually Use HTML (Not Often)

There are exactly two situations where HTML makes sense:

1. You're sending to a warm audience that already expects it.

If someone signed up for your newsletter and they're expecting branded emails, HTML is fine. That's not cold email - that's nurture. The dynamics are completely different.

2. You're testing with a specific decision maker who loves visuals.

If you're doing outreach to architects, designers, or creative directors, and you have a genuinely visual product, an HTML email with screenshots or a clean layout might make sense for a small test segment. Even then, I'd start with plain text, prove it works, and only use HTML if you can show it outperforms for that specific audience.

That's it. Those are the exceptions.

The Actual Format That Works

Here's what a high-performing plain text email looks like:

Subject: Quick question about [Company Name]

Body:

Hey [First Name],

I was looking at [Company Name]'s website and noticed [specific, non-generic observation about their business].

We help [type of business similar to theirs] fix [specific problem they likely have]. One of our clients, [similar company name], went from [metric] to [metric] in [timeframe].

Might be worth a 15-min call to see if we could do something similar for you?

Let me know.

[Your name]
[Phone number]

That's it. No formatting. No colors. No fancy signature. No images. No buttons.

Does it look boring? Yes. Does it work? Also yes.

The HTML Email Mistake We See Constantly

Companies send HTML emails with:

None of that increases reply rate. It does the opposite. Every visual element screams "automated marketing campaign." You're fighting against your own email format.

If you're going to use HTML, use it minimal. No logo. No footer links. Basic text styling at most. But honestly - just use plain text instead.

Plain Text Doesn't Mean Sloppy

Plain text is clean. It's structured. It has short paragraphs. It gets to the point in under 75 words. It has one clear ask.

You're not writing an email that looks plain - you're writing an email that IS plain. The writing quality and clarity matter more than the formatting ever will.

This connects directly to how to write cold emails that actually get replies. The format is secondary. The message is primary.

The Setup That Actually Wins

Use plain text. No exceptions for cold outreach. Configure your email sending platform to use plain text by default. Make sure your CRM or cold email tool isn't auto-formatting anything into HTML.

If you're using tools like lemlist, make sure you have the plain text version set up properly. Most people set up HTML and forget about the plain text tab - then wonder why their deliverability is lower than expected.

Send test emails to yourself in different email clients - Gmail, Outlook, Apple Mail. Make sure they look good as plain text everywhere. They will.

Then track your reply rate. If you're not seeing 4%+ replies on properly executed campaigns with good lists and solid copy, something else is off - probably your list quality or your deliverability setup.

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