D-Link NetDefendOS User Manual page 528

disabled by default and this is the recommended setting.
• Block USER/PASS Commands
This blocks clients sending their credentials in plain text.
SMTP Options
The following options are available for SMTP traffic only:
• Maximum email rate
This option is available for SMTP only and is the maximum number of emails per second that
will be accepted.
• Maximum email size
This option is available for SMTP only and is the maximum size of an email that is acceptable.
Whitelist/Blacklist
One or more Email Filter objects can be added as children to an Email Control Profile object. Each
filter specifies one address or, using wildcards, a series of addresses that are to be always
dropped (blacklisted) or always allowed (whitelisted).
The wildcard asterisk ("*") character can be used to specify any string. For example, the string
*.@example.com represents any email address from the example.com domain. The question mark
("?") character can also be used to represent any single character.
Whitelisting and blacklisting takes precedence over all other email filtering. Whitelisted emails
will never be subject to anti-spam or anti-virus processing if either of those is enabled.
If an email comes from a blacklisted domain, the mail is not dropped. Instead, the subject line has
a configurable text string inserted at the beginning. By default, this string is:
However, this text can be set by the user, as previously described.
Anti-Spam and Filter Scoring
The anti-spam feature of email filtering using IP policies must be explicitly enabled in the Email
Control Profile object used with an IP policy. Once enabled, a score is calculated by adding
together the sub-scores of the enabled anti-spam filters. The score is used in the following ways:
• If the total score is equal to or greater than the specified Tagging Threshold (the default
value is 10) then an email is considered to be SPAM and tagged as such.
• For SMTP only, if the total score is equal to or greater than the specified Reject Threshold
(the default value is 20) then an email is dropped.
Each anti-spam filter can be enabled or disabled and they are comprised of the following list:
• Domain Verification
*** BLACK LISTED ***
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Chapter 6: Security Mechanisms