Legal analysis: it is generally understood that a contract that is not signed by me should be invalid. But if you authorize others to sign relevant contracts on your behalf, the actions taken by the agent within the scope of authorization have the same legal effect as those taken by me. Another exception is agency by estoppel. When the other party to a contract has reason to believe that the other party has the right to act as an agent, the contract signed by it also has legal effect.

Legal basis: Civil Code of People's Republic of China (PRC).

Article 162 A civil juristic act carried out by an agent in the name of the principal within the scope of his agency authority is effective for the principal.

Article 172 If the actor has no agency right, exceeds the agency right or the agency right is terminated, and the counterpart has reason to believe that the actor has the agency right, the agency act is valid.