Is sending plain text safer than HTML?

You might have heard this one before: "Switch to plain text and you'll land in the inbox." It sounds logical. Spam often looks like flashy HTML. Personal emails are usually plain text. So plain text must be safer, right?

Not quite. Plain text isn't inherently safer than HTML for deliverability. Both formats reach the inbox just fine when you're a legitimate sender with solid authentication behind you. The format itself isn't what filters care about most.

What spam filters actually evaluate is your sender reputation, your authentication setup (SPF, DKIM, DMARC), your engagement history, and how many complaints your emails generate. A beautifully coded HTML email from a trusted sender will outperform a plain text email from a sketchy domain every single time.

Where HTML can actually cause problems

The myth has a grain of truth in it. HTML does introduce more ways to mess things up. Here's what actually triggers filters:

• Broken or malformed HTML. Unclosed tags, mismatched elements, messy code copied from Word or Google Docs. Filters notice when the structure is a mess.
• Excessive image-to-text ratio. If your email is mostly images with almost no text, filters get suspicious. One big image with a call-to-action link is a classic spam pattern. (More on this in the images question.)
• Hidden text. White text on a white background, tiny font tricks, display:none on keyword-stuffed content. Filters are trained to catch this.
• Suspicious link structures. Redirect chains, URLs that don't match the visible link text, or links pointing to flagged domains.
• Inline CSS overload. Overly complex styles that look like they're trying to obscure something.

Well-built HTML from a reputable sender doesn't hit any of those. And most modern ESPs like Mailchimp or Klaviyo generate clean HTML by default, so you're not usually writing raw code from scratch.

When to actually choose plain text

Plain text has real advantages, but they're strategic rather than deliverability-driven.

Use plain text when you want the email to feel personal. A cold outreach email, a one-on-one follow-up, or a short transactional notice often lands better as plain text because it reads like a real message from a real person. Readers respond to that. Replies go up. Complaints go down. That does help your reputation over time, but it's the engagement effect, not the format itself, that moves the needle.

Use HTML when you need structure, branding, or visual hierarchy. Newsletters, promotional emails, product announcements, and anything where you want buttons, images, or branded layouts should use HTML. Trying to do that in plain text just makes your email harder to read.

Still some senders send both at once, which is the right call. A properly built multipart MIME email includes both a plain text and an HTML version. The recipient's email client picks whichever it can display. This is considered best practice regardless of your audience.

The bottom line: don't strip your HTML to chase some deliverability shortcut. Fix your authentication, keep your list clean, and write emails people actually want to open. That's what moves your sender reputation in the right direction.

Not sure if your authentication is set up correctly? Run your domain through our free SPF checker to start. Or if something's broken and you need a human, our SOS hotline is free.