The legal person's signature could not be found by mailing the compulsory resignation notice.

In this case, I suggest you contact the courier company to verify the delivery. If the courier company confirms that the mail has been delivered and signed, you can ask the company for the information of the signer to confirm whether it is signed by your legal representative. If the signatory is indeed your legal representative, the notice has come into effect and has legal effect. If the recipient is not your legal representative, you can contact the courier company to investigate and prepare relevant evidence to claim compensation from the company.

If the courier company can't provide the information of the consignee, it can apply to the court for re-delivery. In the process of redelivery, the court will take appropriate measures to ensure that the notice reaches the correct address. If the re-service still fails, you can apply to the court for direct announcement service.

Finally, in order to avoid similar situations, it is suggested that you choose a traceable courier service when sending important documents, and indicate the recipient's name and telephone number at the recipient's address to ensure that the courier company can contact the recipient and sign for it. At the same time, other ways can be considered, such as mailing and registered mail or using email.