Cisco Cisco Email Security Appliance C690 User Guide

If you suspect problems with delivering email from the appliance, try the 
following strategies:

Determine if the problem is domain-specific.

Use the 

tophosts

 command to get immediate information about the email 

queue and determine if a particular recipient domain has delivery problems. 

Are there problem domains returned when you sort by “Active Recipients?” 

When you sort by Connections Out, does any one domain reach the maximum 
connections specified for a listener? The default maximum number of 
connections for a listener is 600. The default maximum system-wide number 
of connections if 10,000 (set by the 

deliveryconfig

 command). You can 

examine the maximum number of connections for a listener using the 
command:

listenerconfig

 -> 

edit

 -> injector_number -> 

limits

Are the connections for a listener further limited by the 

destconfig

 command 

(either by system maximum or by Virtual Gateway addresses)? Use this 
command to examine the 

destconfig

 connection limits: 

destconfig

 -> 

list

Use the 

hoststatus

 command. 

“Drill-down” using the 

hoststatus

 command on the top domains listed from 

the results listed by the 

tophosts

 command. 

Is the host available and accepting connections? 

Are there problems with one specific MX record mail server for the given 
host? 

The 

hoststatus

 command reports the last “5XX” status code and description 

returned by the host if there is a 5XX error (Permanent Negative Completion 
reply) for the specified host. If the last outgoing TLS connection to the host 
failed, the 

hoststatus

 command displays the reason why it failed.

Configure and/or examine the domain debug, bounce, and text mail logs to 
check if the recipient host is available.

Domain debug logs record the client and server communication during an 
SMTP conversation between the appliance and a specified recipient host. 
This log file type can be used to debug issues with specific recipient hosts.