Plain Text vs HTML Email: Which Should You Send?
It's not really either/or. Here's how plain text and HTML email actually differ on deliverability and engagement — and why you should send both.
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Overview
The plain text vs HTML email debate is mostly a false choice: well-built emails are multipart, carrying both a plain-text and an HTML version so each client shows the best one it can. The real question is which to emphasize, and that depends on the email. Cold, one-to-one-feeling outreach often does better looking like plain text; a branded newsletter or promotion usually needs HTML. Here's how they actually differ.
How the two formats actually differ
HTML email buys you design, branding, images, and reliable click tracking — essential for newsletters, promotions, and anything where layout carries meaning. The costs: more weight, rendering quirks across clients (especially Outlook), and a "marketing" feel that can nudge spam filters when it's image-heavy and link-stuffed. Plain text is the inverse: lightweight, renders identically everywhere, no tracking, and it reads like genuine one-to-one mail — which is exactly why cold outreach leans on it.
The deliverability myth worth killing: plain text is not inherently more "inbox-safe." A clean, relevant message from an authenticated domain lands either way. What hurts is a bad text-to-image ratio, link shorteners, and — importantly — HTML with no plain-text part at all. The format is a smaller factor than authentication, reputation, and relevance.
- HTML: design, branding, click tracking — best for newsletters/promos
- Plain text: personal, universal, no tracking — best for cold/1:1
- Image-heavy, link-stuffed HTML can nudge spam filters
- Authentication and relevance matter far more than format
| HTML | Plain text | |
|---|---|---|
| Design & branding | Yes | No |
| Click/open tracking | Yes | No |
| Feels personal | Less | More (1:1 mail) |
| Best for | Newsletters, promotions | Cold outreach, personal follow-ups |
What to actually send: multipart
The real answer is rarely either/or — send multipart MIME, which packages both a plain-text and an HTML version in one message so each client renders the best it supports. This isn't optional polish: an HTML-only email with no text alternative is a recognized mild spam signal, so a proper plain-text part actively helps deliverability. Get that right and the "debate" is just a styling choice.
Then match the emphasis to the goal: rich, branded HTML for newsletters and campaigns; plain-text-style (multipart, but minimal design and few links) for cold outreach and personal follow-ups, because it reads human. Good tools generate and sync the plain-text part for you — Mailbase's MJML campaigns produce responsive HTML with a text alternative automatically, so you never ship HTML-only by accident.
- Always send multipart (HTML + a real plain-text part)
- HTML-only with no text part is a mild spam signal — avoid it
- Rich HTML for newsletters; plain-text feel for cold/1:1
- Let your tool generate and sync the plain-text part
Common mistakes
- Using modern CSS layout that Outlook silently breaks (use tables).
- Shipping HTML-only emails with no plain-text part — a spam signal.
- Forgetting alt text and a fallback for when images are blocked.
- Not testing on a real phone and in Outlook before sending.
Sources and further reading
Official docs for current setup details, pricing, and API behavior — verify specifics there, since they change.
Related guides
More on plain text vs html email and the surrounding email design workflow: