Do plain text cold emails always inbox better?

Here's a belief that's deeply embedded in cold email culture: plain text emails land in the inbox more reliably because they look less like marketing. It sounds logical. It's mostly wrong.

Spam filters don't really care whether your email has a header image or not. They care about your sender reputation, whether your domain is properly authenticated, and whether recipients are actually engaging with your emails or hitting the spam button. A plain text email from a domain with no SPF or DKIM will fail just as fast as a fancy HTML one. A well-authenticated sender with a clean reputation delivers fine regardless of format.

That said, plain text does have a real advantage for cold outreach. It reads more like a personal note and less like a campaign. That perception can improve reply rates, which in turn builds engagement signals. Engagement signals do influence deliverability over time. So there's an indirect benefit, just not the direct inbox filter bypass that most people assume.

HTML cold emails aren't automatically a problem either. A clean, minimal HTML email from a domain that passes SPF, DKIM, and DMARC will deliver fine. The format itself isn't what triggers filters. Spammy content, excessive links, misleading subject lines, and poor domain reputation are what get you filtered.

So pick your format based on what fits your outreach style. Plain text works well for one-to-one prospecting where a personal feel matters. Minimal HTML is fine for outreach that needs a little structure or a single clear call to action. Neither format is a shortcut past the fundamentals.

If you're seeing cold emails land in spam and wondering whether format is the culprit, it almost certainly isn't. Check your authentication records first. You can run a quick check on your domain with our free SPF checker, or if things look broken and you need a second pair of eyes, our SOS hotline is free.