Symantec Mail Security, Administration Manual

Page: 99 / 258

99 Configuring email filtering
Managing Email Firewall policies
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IP-based: specify IP connections
Symantec Mail Security for SMTP checks the IP address of the mail server
initiating the connection to verify if it is on your Allowed Senders Lists or
Blocked Senders Lists. Wildcards are not supported. Although you can use
network masks to indicate a range of addresses, you cannot use subnet
masks that define non-contiguous sets of IP addresses (e.g. 69.84.35.0/
255.0.255.0). Supported notations are:
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Single host: 128.113.213.4
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IP address with subnet mask: 128.113.1.0/255.255.255.0
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Classless Inter-Domain Routing (CIDR) IP address: 192.30.250.00/18
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Third party services: supply the lookup domain of a third party sender
service
Symantec Mail Security for SMTP can check messages sources against third
party DNS-based lists to which you subscribe, for example, list.example.org.
Automatic expansion of subdomains
When evaluating domain name matches, Symantec Mail Security for SMTP
automatically expands the specified domain to include subdomains. For
example, Symantec Mail Security for SMTP expands example.com to include
biz.example.com and, more generally, *@*.example.com, to ensure that any
possible subdomains are allowed or blocked as appropriate.
Logical connections and internal mail servers: non-gateway deployments
When deployed at the gateway, Symantec Mail Security for SMTP can reliably
obtain the physical or peer IP connection for an incoming message and compare
it to connections specified in the Allowed Senders Lists and Blocked Senders
Lists. If deployed elsewhere in your network, for example, downstream from the
gateway MTA, Symantec Mail Security for SMTP works with the logical IP
connection. Symantec Mail Security for SMTP determines the logical connection
by obtaining the address that was provided as an IP connection address when
the message entered your network. Your network is based on the internal
address ranges that you supply to Symantec Mail Security for SMTP when
setting up your Scanners. This is why it is important that you accurately identify
all the internal mail hosts in your network. For more information, see
“Advanced SMTP settings” on page 25.
Adding senders to Blocked Senders Lists
To prevent undesired messages from being delivered to inboxes, you can add
specific email addresses, domains, and connections to your Blocked Senders
Lists.