A digital signature certificate carries with it the personal identification of the signer which includes an e-mail address as well. An RSA algorithm creates a unique set of keys called the public key and private key for a digital signature certificate. The public key is used to encrypt the message in the e-mail.
The recipient of the email uses a matching private key to decrypt the e-mail. These keys are issued to the signer after authenticating the e-mail address. Therefore, the change or addition of email addresses is not possible. However, an individual or organization can obtain two digital signature certificates associated with a single e-mail address.
You can also get an additional digital signature certificate for a different email account. It can be either for personal or professional use. Users can register for a digital signature certificate on eMudhra, a licensed certifying authority by the government of India. Users can verify their identity online within 5 minutes and download their digital signature certificate within 30 minutes.