Google Message Encryption Administration Guide - Manual (Page 45)

46 Postini Encryption Services Administration Guide
The first time the user opens a message, the user will be prompted to add a
password.
On subsequent messages, the user is prompted to enter that password to read
the message.
Key information is stored by Inbox Delivery in a separate server used to manage
keys for decrypting messages. The browser connects to that server to update
password information and verify keys.
Depending on the recipient’s browser settings, passwords are also stored as
cookies on the recipient’s local browser.
If the user forgets the password, a “Forgot Your Password?” link is available,
which allows the user to send a new message to create a new password.