The fourth argument is the expected result of the lookup. For the lookup host
dialups.mail-abuse.org, a successful lookup (one that means the message should be
rejected) will return the address 127.0.0.3. Different lookup hosts will return different
addresses on success, so you will need to visit the appropriate web site to determine
the address to match. If the address is omitted from the FEATURE(enhdnsbl), any
successfully returned address will cause the message to be rejected.
If more than one address can be returned, you can list up to five more following the
first one. In the following, we list three possible returned addresses (the line is
wrapped to fit the page):
FEATURE(enhdnsbl,`dialups.mail-abuse.org??, `"550 dial-up site refused"??,
,`127.0.0.1.??,
`127.0.0.2.??, `127.0.0.3.??)
Here, if any of the three addresses is returned, the message will be rejected. Note that
if you don??™t know specifically what will be returned, you can use rule LHS-operators
(?§18.2) in place of specific numbers. For example, instead of the three addresses
shown earlier, you can specify one like this:
FEATURE(enhdnsbl,`dialups.mail-abuse.org??, `"550 dial-up site refused"??, ,`127.0.0.$-
.??)
Here, the $- will match any number in that position. If you need to restrict the range
of acceptable values you can use a class, perhaps like this:
LOCAL_CONFIG
C{OneTwoThree}1 2 3
FEATURE(enhdnsbl,`dialups.
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