Cisco Cisco Email Security Appliance C160 Guía Del Usuario
2-5
Cisco IronPort AsyncOS 7.5 for Email Advanced Configuration Guide
OL-25137-01
Chapter 2 Configuring Routing and Delivery Features
SMTP Routes and DNS
Use the special keyword
USEDNS
to tell the appliance to do MX lookups to
determine next hops for specific domains. This is useful when you need to route
mail for subdomains to a specific host. For example, if mail to example.com is to
be sent to the company’s Exchange server, you might have something similar to
the following SMTP route:
mail for subdomains to a specific host. For example, if mail to example.com is to
be sent to the company’s Exchange server, you might have something similar to
the following SMTP route:
example.com exchange.example.com
However, for mail to various subdomains (foo.example.com), add an SMTP route
that looks like this:
that looks like this:
.example.com USEDNS
SMTP Routes and Alerts
Alerts sent from the appliance to addresses specified in the System
Administration > Alerts page (or the
Administration > Alerts page (or the
alertconfig
command) follow SMTP
Routes defined for those destinations.
SMTP Routes, Mail Delivery, and Message Splintering
Incoming: if one message has 10 recipients and they are all on the same Exchange
server, AsyncOS will open one TCP connection and present exactly one message
to the mail store, not 10 separate messages.
server, AsyncOS will open one TCP connection and present exactly one message
to the mail store, not 10 separate messages.
Outgoing: works similarly, but if one message is going to 10 recipients in 10
different domains, AsyncOS will open 10 connections to 10 MTAs and deliver
them one email each.
different domains, AsyncOS will open 10 connections to 10 MTAs and deliver
them one email each.
Splintering: if one incoming message has 10 recipients and they are each in
separate Incoming Policy groups (10 groups), the message will splinter even if all
10 recipients are on the same Exchange server. Thus, 10 separate emails will be
delivered over a single TCP connection.
separate Incoming Policy groups (10 groups), the message will splinter even if all
10 recipients are on the same Exchange server. Thus, 10 separate emails will be
delivered over a single TCP connection.