Cisco Cisco Email Security Appliance C160 Mode D'Emploi

If the “Required” setting for either IPv4 or IPv6 is specified, the appliance will negotiation a connection 
to the domain using an address of the specified version. If the domain doesn’t use that IP address version, 
no email will be sent. If the “Preferred” setting for either IPv4 or IPv6 is specified, the appliance will 
first attempt to negotiation a connection to the domain using an address of the specified version then fall 
back to the other if the first is not reachable.

You may want to limit how your appliance will deliver email to avoid overwhelming remote hosts or your 
own internal groupware servers with email from your appliance. 

For each domain, you can assign a maximum number of connections, outbound messages, and recipients 
that will never be exceeded by the system in a given time period. This “good neighbor” table is defined 
through the Destination Controls feature (Mail Policies > Destination Controls or the 

destconfig

 

command — previously the 

setgoodtable

 command). You can specify the domain name using the 

following syntax: 

domain.com

or

.domain.com

This syntax enables AsyncOS to specify destination controls for sub-domains such as 
sample.server.domain.com without entering each full subdomain address individually.

For connections, messages, and recipients, you set whether the limits you define are enforced for each 
Virtual Gateway address, or for the entire system. (Virtual Gateway address limits control the number of 
concurrent connections per IP interface. System-wide limits control the total number of connections the 
appliance will allow.) 

You also set whether the limits you define are enforced for each MX record of the specified domain, or 
for the entire domain. (Many domains have multiple MX records defined for accepting email.) 

The current system default is 500 connections per domain and 50 messages per connection.

These values are explained in 

. 

The maximum number of outbound connections that will be made by the appliance to 
a given host. (Note that the domain can include your internal groupware hosts.) 

The maximum number of messages allowed for a single outbound connection from the 
appliance to a given host before initiating a new connection.

The maximum number of recipients allowed within the given period of time. “None” 
denotes that there is no recipient limit for the given domain. 

The minimum period of time — between 1 and 60 minutes — that the appliance will 
count the number of recipients. Specifying a time period of “0” disables the feature. 

If you change the recipient limit, AsyncOS resets the counters for all messages 
already in the queue. The appliance delivers the messages based on the new 
recipient limit.