STO Express Co., Ltd. (002468.SZ) is facing a formal investigation by the State Post Bureau, which has also led to the suspension of the company's plan to issue up to 30 billion yuan (approximately $4.11 billion) in convertible bonds. The regulatory body announced on August 4 that it has initiated a probe into the courier company for safety management failures, citing multiple work-related accidents and recurring safety hazards at its facilities. The bureau stated that STO Express Co., Ltd. has failed to implement unified safety management across its operations, a violation of national regulations.

In response to the investigation, STO Express announced it would withdraw its application for the convertible bond issuance. The company had planned to allocate 21.37 billion yuan of the proceeds to upgrade smart logistics equipment and 8.63 billion yuan to enhance its trunk line capacity network, with a total project investment of 47.51 billion yuan. The company admitted to "significant shortcomings" in fulfilling its unified management responsibilities and pledged to cooperate fully with the investigation, vowing to improve safety compliance across its direct operations, franchisees, and suppliers.

The investigation is not the only recent legal development for STO Express. On August 3, 2026, the company received a court ruling permitting plaintiff Xi Chunyang to withdraw his lawsuit. Xi had filed a shareholder qualification dispute in January 2026, seeking ownership of 20,284,236 shares of STO Express currently held by his ex-wife, Chen Xiaoying, who is a co-controlling shareholder of the company. The claimed shares, representing 1.33% of the company's total equity, were valued at nearly 300 million yuan based on the company's closing stock price of 14.32 yuan on the day of the announcement, which gave STO Express a market capitalization of 21.9 billion yuan. The case was initially filed in a Yuhuan court but was later transferred to a Shanghai court, where Xi ultimately withdrew his claims, temporarily ending the dispute.

Xi Chunyang was once a delivery driver for STO Express who rose to become a general manager after driving for the company's late founder, Nie Tengfei. Nie Tengfei, who founded STO Express, died suddenly when the company was at its peak. Chen Xiaoying, Nie's widow, took control and quickly transferred management to her brother, Chen Dejun. This led to a split, with several key figures leaving to establish rival courier companies: Nie's brother founded YTO Express; a former finance employee, Zhang Xiaojuan, co-founded Yunda Express; branch manager Sang Xuejiao founded ZTO Express; and colleague Xu Jianrong founded Best Express, creating what is now known as the "Four Tongs and One Da" (四通一达) group. Fifteen years after Nie's death, Chen Xiaoying married Xi Chunyang, who went on to manage TTK Express, which was later sold to Suning.com.

According to STO Express, Chen Xiaoying and Xi Chunyang divorced in 2012, and the lawsuit was a dispute over the division of property from that divorce. Xi's decision to sue more than a decade later and then withdraw the case within six months has surprised many outside observers. As of March 31, 2026, the major shareholders of STO Express included Zhejiang Cainiao Supply Chain Management Co., Ltd. (25%), Shanghai Gongzhirun Industrial Development Co., Ltd. (16.1%), and Shanghai Deyin Investment Holding Co., Ltd. (7.76%). Chen Dejun and Chen Xiaoying, along with their affiliated entities, control a total of 35.85% of the company's shares.