The email from Alphabet Inc. Class C (GOOGL.US) has become a key piece of evidence in the antitrust trial.

According to foreign media reports, the US government has filed an antitrust lawsuit against Alphabet Inc. Class C (GOOGL.US) advertising business, with prosecutors using internal emails from Alphabet Inc. Class C as key evidence to prove that company executives were aware of Alphabet Inc. Class C's dominant position in the online advertising market. In the past two weeks of the trial, evidence submitted by the Justice Department included an email from Neal Mohan, the Chief Executive Officer of YouTube in 2010. Mohan previously oversaw Alphabet Inc. Class C's display advertising business. At that time, Alphabet Inc. Class C was facing greater competition from advertising technology startups. Mohan wrote in an email to his colleagues at Alphabet Inc. Class C, "One way to ensure that we do not fall further behind in the market is to pick the most attractive product and park it somewhere." In 2011, Alphabet Inc. Class C spent $400 million to acquire advertising technology company AdMeld and two years later integrated the technology of this startup into Alphabet Inc. Class C's advertising exchange platform AdX, before eventually shutting down the company. Prosecutors claim that the AdMeld deal was part of a broader strategy to eliminate competitors and lock in customers with terms requiring them to pay for software tools in order to access another software tool. On the witness stand, Mohan denied that his recommendation to acquire AdMeld was to eliminate competitors. He stated that the acquisition was more beneficial for customers as it filled a gap in the product suite. Reportedly, prosecutors also questioned the emails of former Alphabet Inc. Class C executives including Jonathan Bellack, Chris LaSala, and Isar Lipkovitz. Other witnesses included former News Corp executive Stephanie Lazer and Alphabet Inc. Class C clients, with Lazer testifying that she felt she had no choice but to use Alphabet Inc. Class C's platform as switching ad servers would cost millions of dollars in ad revenue. The legal team for Alphabet Inc. Class C will present their defense next week. US District Judge Leonie Brinkema in Virginia will make a ruling on the case. A ruling against Alphabet Inc. Class C could potentially result in the company selling off part of its advertising technology business, a business estimated to be worth $100 billion or more.