User Guide

19-3
AsyncOS 9.1.2 for Cisco Email Security Appliances User Guide
Chapter 19 S/MIME Security Services
S/MIME Security Services in Email Security Appliance
Organization A sending a message to Organization B:
1. Bob (Organization A) uses an email client to send an unsigned and unencrypted message to Dave
(Organization B).
2. Email Security appliance in the Organization A signs and encrypts the messages and sends it to
Organization B.
3. The third-party application at the gateway of Organization B decrypts and verifies the message.
4. Dave receives an unencrypted and unsigned message.
Organization B sending a message to Organization A:
1. Dave (Organization B) uses an email client to send an unsigned and unencrypted message to Bob
(Organization A).
2. The third-party application at the gateway of Organization B signs and encrypts the message and
sends it to Organization A.
3. Email Security appliance in the Organization A decrypts and verifies the message.
4. Bob receives an unencrypted and unsigned message.
Scenario: Business-to-Consumer
Organizations A and B want all the messages communicated between them to be signed and encrypted
using S/MIME. Organization A has configured Email Security appliance to perform S/MIME security
services at the gateway level. Organization B has configured the email clients of all the users to perform
S/MIME security services.
Organ izat ionB
OrganizationA
EmailClient
EmailSecurityAppliance
EmailClient
Gateway
Alice
Erin
Legend
Messagefrom
AtoB
Messagefrom
BtoA