The Ningxi Xu Family only had one source for their secret messages, which was the current Family Head, Xu Jingfeng.
In the letter, Xu Jingfeng mentioned that both merchant caravans had already arrived at Han Yang Pass and had also received the pre-ordered grains. However, just as they were about to leave the pass, they were suddenly hit with an embargo order stating that without the permission of the garrison, no large quantities of grains were allowed to be transported privately out of the pass. Only the official army-escorted merchant caravans could transport grains; private caravans were strictly forbidden from transporting grains.
Wei Yuan knew that Xu Zhongxing, who was in charge of the garrison, belonged to the Xu Family, and his blood relation to Xu Jingfeng was not that distant. The Ningxi Xu Family had always been able to freely transport various contraband items, and routine resources like grain were never an issue.