Short seller Andrew Left announced a new target, and the company's stock tanked

Screenshot, CNBC

Andrew Left, a short seller whose targets have included Valeant and Mobileye, released a report saying that he has identified another short, and the company's stock is tanking.

Left, the founder of Citron Research, released a 21-page report on technology company j2 Global. In it, he said that the company's growth has "hit a wall" and issued a price target of $27.

Left notes that j2's main business is fax-to-email, or "eFax," services. According to the company's filings, eFax services make up over 40% of its revenues.

He said that not only is eFax a dying business, but j2 Global's proprietary technology that has dominated the market is rolling off patent protection. The company's core eFax patent expires on April 1, 2017, according to Left.

"After spending a decade suing, then buying competitors who could have undercut pricing in a race to the bottom (which is 'free') j2 has hit a wall in the acquisition game at the same moment their patent protection is expiring," said Left's report.

Additionally, in order to distract investors from the dependence on eFax revenue, the company has listed these services under the banner of cloud computing in order to appear more palatable, according to Left.

"Putting aside digital media, which we will discuss below, everything bought for j2's 'cloud computing portfolio' aside from fax-to-email is commoditized, unprofitable junk, with no new or unique technology and no leverage," said the report. "The only thing cloudy about this is appearances."

In the end, Left said that the company is worth much less than its current valuation.

"It is Citron's opinion that j2 Global has spent the past four years using the money generated by its legacy eFax business to prop the financials of a collection of unremarkable and/or useless assets that have all been acquired with terms undisclosed," concluded the report.

After the release of the report, j2 Global's stock nosedived. The stock crashed in trading Thursday, finishing the day down just under 20%, at $56.90 a share.

We have reached out to j2 Global for a response.

Read Left's full report here »

Screenshot, CNBC

NOW WATCH: Apple says this commonly used hack won’t actually make your iPhone battery last longer