The messages from the world’s biggest supertanker owner often begin with pleasantries: “Dear Ladies and Gentlemen.” Within minutes, the WhatsApps are the talk of the oil-tanker industry, a multibillion-dollar corner of the energy market that’s been plunged into chaos by the Iran war this year, and where word of mouth is the main way information spreads.

Iran’s Persian Gulf Strait Authority said it would take “legal action” against tankers belonging to Sinokor, the world’s biggest oil tanker owner that has carried millions of barrels out of the Strait of Hormuz in recent weeks.