Here's one corner of the digital ad world that Google and Facebook don't dominate

If money is spent to hawk something online, chances are it goes through Google or Facebook.

The two have locked down the bulk of digital advertising — an estimated 85 cents of every new dollar spent now — leaving a slew of other companies to fight for the scraps.

But dollars spent advertising to workplaces don’t necessarily go to Google or Facebook. They go to enterprise companies that specialize in what’s typically called “marketing technology,” rather than ad tech. It’s a growing industry — one that Google is looking to edge into.

As are several competitors. One of them, an email marketing company called Adestra, just poached a Google sales exec to lead its effort. Matt McGowan, head of strategy for Google’s ad agency relations, is joining Adestra as president as the London-based company tries to compete with market leaders Adobe, Oracle, Salesforce and IBM.

Those four netted roughly $4 billion of the $5.8 billion spent on enterprise marketing software, according to Forrester. And the first three are clocking 20 percent or more of annual growth. IBM is growing more slowly.

But they’re only reaching huge companies, claims Adestra. “They’re all concentrating very hard on servicing the top end,” said COO Steve Denner. “[Smaller] companies are just getting left behind by the great march to the marketing stack.”

That “stack” is shorthand for a range of services — from analytics to data management and marketing automation software — and Google wants in. The company recently shuffled its sales organization, blending its sizable display ad sales team with its analytics team, which provides Web measurement tools. Then, last month, it launched a new product — the Google Analytics 360 Suite — meant to compete with Adobe and Oracle.

That might not be so easy. These cloud marketing companies have locked customers into their systems over the years.

“These solutions are extremely sticky and hard to displace,” said Ari Paparo, CEO of the ad tech company Beeswax and an industry vet. “The email business is also very mature and difficult for marketers to justify switching.”

Adestra says it has a nice position in that business, claiming 40 percent annual sales growth for the last 10 years. It wouldn’t share revenue numbers, but says it’s profitable and now hiring a competitive sales team.

“We’re looking for people that have been carrying million-dollar accounts for years and hitting them,” said Adestra’s Denner.