A computerized data protection method prevents data of an electronic device from being compromised through e-mail. A digital certificate is installed in the electronic device, and one or more safe e-mail addresses are configured and stored in the digital certificate. Predetermined data stored in the electronic device are correlated with the one or more safe e-mail addresses. When the predetermined data need to be sent to a target e-mail address, whether the target e-mail address matches with one of the safe e-mail addresses is verified. If the target e-mail address matches with one of the safe e-mail addresses, the predetermined data is sent to the target e-mail address.