What you want to ask is to verify the signature with the certificate provided by the sender. How to confirm that the certificate has not been tampered with with with the mail? Verify the digital signature of the certificate and compare the hash values of the certificate.

1. Verify the digital signature of the certificate: the certificate in the mail should have a digital signature. You can use the signer's public key to verify the digital signature to ensure that the certificate has not been tampered with.

2. Compare the hash values of certificates: Hash values are a series of fixed-length strings obtained by calculating the contents of certificates, which can be used to verify the integrity of certificates.