A London email security startup is in talks to sign up Freshfields Bruckhaus Deringer as a client, in what would be the latest major international law firm to buy into the service.

Freshfields has held exploratory talks with Tessian, according to two people close to the matter, although no contract has yet been signed.

If the two go ahead, Freshfields will be the second magic circle firm to become a Tessian client. Clifford Chance is already working with it, two people with knowledge of the firm said, as are U.K. law firms Clyde & Co, Dentons, DAC Beachcroft and Herbert Smith Freehills. Am Law 100 law firm K&L Gates is also a client.

Tessian, a tech startup founded in 2013, uses machine learning technology to identify normal and abnormal email-sending patterns to warn users of potentially nefarious activity on their email accounts, and also recognises phishing attempts.

It raised $42m in a Series-B funding round led by venture capital firm Sequoia last month, as part of its plans to accelerate growth in the U.S. and other markets. This brings the total raised to just under $60m, according to its website. It employs a total of 100 people and opened a New York office last November.