Cisco Cisco Email Security Appliance X1070 用户指南
4-3
Cisco IronPort AsyncOS 7.5 for Email Advanced Configuration Guide
OL-25137-01
Chapter 4 Validating Recipients Using an SMTP Server
Figure 4-1
SMTP Call Ahead Server Conversation Workflow
1.
The sending MTA initiates an SMTP conversation.
2.
The Email Security appliance suspends the SMTP conversation while it sends
a query to the SMTP server to verify the recipient, validuser@recipient.com.
a query to the SMTP server to verify the recipient, validuser@recipient.com.
Note
If SMTP routes or LDAP routing queries are configured, these routes
will be used to query the SMTP server.
will be used to query the SMTP server.
3.
The SMTP Server returns a query response to the Email Security appliance.
MAIL FROM: user@sender.com
RCPT TO: validuser@recipient.com
RCPT TO: validuser@recipient.com
Sending MTA
SMTP Server
START HERE
1
2
3
4
Email Security appliance
Conversation with sending MTA
Conversation with Call-Ahead
Server
Server