Cisco Cisco Email Security Appliance C160 Guida Utente

If there is no LDAP routing query or no SMTP Routes configured for the domain, 
the result of preceding state is passed to next stage. In any case where there is no 
SMTP Route present, a DNS lookup is performed.

When you use an LDAP Routing query for an SMTP call-ahead query and you 
also have SMTP routes configured, the routing behavior depends upon the values 
returned by the routing query.

If the LDAP routing query returns a single hostname without a port, the 
SMTP call-ahead query applies SMTP routes and then performs a DNS 
lookup to determine the IP address of the SMTP server. 

If the LDAP routing query returns a single hostname with a port, the SMTP 
route is used, but the port returned by the LDAP query is used over any ports 
specified in SMTP routes. Then, a DNS lookup is performed to determine the 
IP address of the SMTP server.

If the LDAP routing query returns multiple hosts with or without ports, SMTP 
routes are applied, but the ports returned by the LDAP routing query are used 
over those present in SMTP routes. Then a DNS lookup is performed to 
determine the IP address of the SMTP server. 

 

Checks the domain name.

Checks for LDAP Routing queries.

Checks for SMTP Routes. 

Performs a DNS Lookup (First an MX Lookup is 
performed, followed by an A lookup).