What is the difference between plain text and HTML body parts?
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You've probably noticed: some emails look like designed web pages (colors, images, buttons), and some look like plain typed text. That's the difference between HTML and plain text body parts.
Plain text is just that: plain. No formatting, no colors, no images, no clickable buttons. It's what you'd type in Notepad. Every email client can display it, always. It's lightweight, accessible, and renders instantly.
HTML is where the design happens. Layouts, brand colors, images, clickable buttons, tracking pixels. HTML lets you build emails that look like your website. But not every client renders HTML the same way (or at all), and some recipients explicitly disable HTML for privacy or bandwidth reasons.
Most modern emails include both versions in what's called a multipart/alternative structure. The email client picks which one to show. If the recipient's client can render HTML and they haven't disabled it, they see the HTML version. If not, they see plain text. You send one email, it carries both, and the client decides.
Why this matters: Gmail, Outlook, and Yahoo Mail all render HTML differently. Some corporate email systems strip HTML entirely for security. Some users disable images. If you only send HTML, recipients who can't or won't render it see nothing useful. If you only send plain text, you lose design, branding, and trackable links.
The practical decision: what kind of email are you sending? Transactional emails (password resets, receipts, order confirmations) often work better as plain text or very simple HTML, because they need to be fast, readable, and trustworthy. Marketing emails (newsletters, promotions, announcements) usually need HTML for branding and engagement tracking. Most ESPs (Mailchimp, Brevo, Klaviyo) automatically generate a plain text version from your HTML, but it's worth checking what that fallback actually looks like.
Still a common mistake: ignoring the plain text version entirely. If your HTML email is a giant image with no real text, and your auto-generated plain text says "View this email in your browser," you've just sent an empty message to anyone who can't see HTML. Always preview both versions before sending.
One more thing: plain text isn't just a fallback. Some senders intentionally use plain text for certain campaigns because it feels more personal and less "marketing." No design, no tracking pixel, just a message. For cold outreach or personal newsletters, that can actually increase engagement. (Of course, you lose click tracking and any visual branding, so it's a trade-off.)
If you want to see what both versions of your email actually contain, paste the raw email source into our Source Analyzer. It'll show you both the plain text and HTML parts, plus how they're structured. Most ESPs let you preview both, but seeing the raw MIME structure is the only way to catch issues like missing plain text or broken multipart boundaries.
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