A method to provide secure transport of email is called ....................
A method to provide secure transport of email is called PGP (Prettey Good Privacy).
Pretty Good Privacy (PGP) is an encryption program that provides cryptographic privacy and authentication for data communication. PGP is used for signing, encrypting, and decrypting texts, e-mails, files, directories, and whole disk partitions and to increase the security of e-mail communications.
PGP stands for “Pretty Good Privacy,” and it's most often used for sending encrypted messages between two people. PGP works by encrypting a message using a public key that's tied to a specific user; when that user receives the message, they use a private key that's known only to them to decrypt it.
The RSA version, for which PGP must pay a license fee to RSA, uses the IDEA algorithm to generate a short key for the entire message and RSA to encrypt the short key. The Diffie-Hellman version uses the CAST algorithm for the short key to encrypt the message and the Diffie-Hellman algorithm to encrypt the short key.