Is the word “Free” a spam trigger?

You've probably heard it a hundred times: "Never use the word 'free' in your subject line or you'll land in spam." It's one of the most persistent myths in email marketing. And it's wrong.

The idea comes from the early days of spam filtering, when filters literally scanned emails for suspicious words. If your subject said "FREE PILLS" or "FREE MONEY," a keyword list flagged you. That was the 1990s. Filters have come a long way since then.

Modern spam filters use machine learning. They're looking at dozens of signals at once: your sender reputation, your engagement rates, whether your authentication is properly set up, how many complaints you're getting, and yes, your content. But "free" as a standalone word in context? That's not going to sink you.

Think about it this way. Mailchimp sends you emails with "free trial" in the subject. Airlines send "earn free miles" campaigns to millions of subscribers every day. Retailers use "free shipping" in subject lines constantly. None of them are automatically landing in spam because of that one word. They're landing in inboxes because their subscribers actually want those emails.

That's the real signal spam filters care about. If your subscribers open your emails, click, and don't complain, a filter isn't going to penalize you for using a normal English word. If your subscribers ignore you, mark you as spam, and your authentication is a mess, no amount of careful word choice will save you.

The myth persists because it's simple. "Avoid this word" is easier advice to follow than "build genuine engagement over time." (Of course, the easier advice is rarely the right one.)

So go ahead and tell people about your free trial, free shipping, or free webinar. Just make sure the people receiving that email actually want to hear from you. That's what moves the needle.

Curious what else you've been warned about that might not hold up? Check out whether "Buy Now" is actually dangerous next.