Editing Email client (section)

===Encryption of the message body===
There are two main models for managing cryptographic keys. [[S/MIME]] employs a model based on a trusted [[certificate authority]] (CA) that signs users' public keys. [[OpenPGP]] employs a somewhat more flexible ''[[web of trust]]'' mechanism that allows users to sign one another's public keys. OpenPGP is also more flexible in the format of the messages, in that it still supports plain message encryption and signing as they used to work before [[MIME]] standardization.

In both cases, only the message body is encrypted. Header fields, including originator, recipients, and often subject, remain in plain text.