Cisco Cisco Web Security Appliance S670 User Guide

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I R O N P O R T   A S Y N C O S   6 . 3   F O R   W E B   U S E R   G U I D E  

C O N F I G U R I N G   S M T P   R E L AY   H O S T S

AsyncOS periodically sends system-generated email messages, such as notifications, alerts, 
and IronPort Customer Support requests. By default, AsyncOS uses information listed in the 
MX record on your domain to send email. However, if the appliance cannot directly reach the 
mail servers listed in the MX record, you must configure at least one SMTP relay host on the 
appliance.

You might want to configure an SMTP relay host in the following scenarios:

• You want the system-generated emails to go to a non-local email address, and port 25 is 

blocked to outside networks.

• Your mail servers do not allow direct port 25 traffic from internal hosts.

If no SMTP relay host is defined, AsyncOS delivers directly to the mail server for each email 
address.

Note — If the Web Security appliance cannot communicate with the mail servers listed in the 
MX record or any of the configured SMTP relay hosts, it cannot send email messages and it 
writes a message in the log files. 

You can configure one or more SMTP relay hosts. You might want to configure multiple SMTP 
relay hosts for redundancy in case one system becomes unavailable. When you configure 
multiple SMTP relay hosts, AsyncOS uses the topmost available SMTP relay host. If an SMTP 
relay host is unavailable, it tries to use the one below it in the list.

You can configure the SMTP relay host from either the web interface or command line 
interface:

• Web interface. Use the Network > Internal SMTP Relay page.

• Command line interface. Use the 

smtprelay

 CLI command.

Use the Network > Internal SMTP Relay page.

To configure the SMTP relay host from the web interface:

1. Navigate to the Network > Internal SMTP Relay page, and click Edit Settings.