The email subject line is dying.

Go ahead: Clench your fist, curse, tell me I’m wrong. There are, after all, 35 million search results for “subject line best practices” and another 28 million for “subject line strategy.” You can use those figures in your argument, but they don’t mean a thing.

Here’s why: Success in email is now driven by visuals.

For more than a few years now, digital marketers have been talking about the impact images have on spurring customers to action—more likes on Facebook, higher click rates on Twitter, more conversions on CTAs, etc.

This isn’t just common sense. There’s science to it. We remember images, especially ones that inspire some emotion, via the limbic portion of our brain. And that’s responsible for our true actions and motivations. It’s the difference between a click to a bounce and a click to convert. (If you’re looking for proof of the visual web’s growing impact on ecommerce, by the way, look no further than our latest EQ, which was released earlier this month.)

So, if images are that successful, why aren’t we focused on them in email? Well, for one, no one gave us a reason to be and we’re all getting tired of seeing little airplanes, stars and or letter art in our subjects. These are now feeble attempts at drawing our attention.

But this is all changing.

Google announced earlier this spring that it was field testing an overhaul to their Promotions tab in Gmail to give it a more Pinterest-like feel. And unroll.me, an email management platform start-up that takes a similar visual approach, announced in January that it has more than 100,000 active users.

The once-mighty subject line is now last in a list of three items a user sees when reviewing email, and unroll.me is making the unsubscribe quick, clean and easy (I unsubscribed to 15 different newsletters in minutes this month alone). The message’s main image is first, the sender is second. And, third, at a 12pt font, is the subject line.

If they’re not signals that marketers needed to think big picture when it comes to email and focus on the real relationship they’re building, I’m not sure what is.

Then there’s this:

Even if you’re dismissive of Gmail’s field test and unroll.me’s success, you can’t be dismissive of what this reality looks like.

Tell me you want to be one of the two brands in this tile that doesn’t have a compelling image displayed in the first moment of viewing this tab. You can’t. You know why? Because your email is invisible. None of the early adopters of visual email are going to see your offer, click on your email or make the conversion you want them to make.

Soon enough, it won’t be a small minority of your customer base being affected. It’ll be a majority.

Unroll.me works with Gmail, Outlook.com (including Hotmail, MSN, & Windows Live), Yahoo! Mail, AOL Mail, and iCloud. Gmail is the third largest email client, only behind Apple’s iPhone and Outlook (which is already aggregating user’s attached images; so you’re sure to see something visually focused from them soon enough).

Email, at first glance, is going to be about being seen, not being read. That’s the future—and it’s clearly within sight.