Myth: Plain text emails always have better deliverability than HTML. True or False?

False. Plain text emails don't automatically land in the inbox more reliably than HTML. The format isn't what spam filters care about most. What they care about is whether you're a legitimate sender with good authentication, a healthy list, and engaged subscribers.

This myth probably spread because poorly built HTML can sometimes cause issues. Think of emails with broken tags, excessive inline styles, or giant image blocks with no text. That kind of HTML can raise flags. But that's a code quality problem, not a format problem. Clean, well-structured HTML causes no deliverability issues at all.

So when does plain text actually make sense? Mostly for context, not filters. A cold sales outreach email feels more personal in plain text. A one-to-one reply from a founder reads better without brand templates. Some B2B audiences genuinely prefer it. These are audience and tone decisions, not deliverability ones.

HTML makes sense any time you need branding, images, clickable buttons, or tracking. Newsletters, promotional campaigns, onboarding sequences, and receipts all benefit from it. Readers expect it. Mailbox providers like Gmail and Outlook handle HTML perfectly well, and they've done so for a long time.

The best of both worlds is a multipart/alternative email. That's when you send both a plain text version and an HTML version in the same message, and the receiving client picks whichever it can render. Most ESPs like Mailchimp and Brevo generate the plain text version automatically when you build an HTML email. It's worth checking that your plain text version actually reads well rather than being a wall of raw code.

The bigger deliverability factors are always your sender reputation, your authentication records, and how your subscribers actually engage with what you send. A plain text email from a poor sender with a bad list will still land in spam. An HTML email from a trusted sender with strong engagement will land in the inbox.