first &%domains%& setting above generates the second setting, which therefore
causes a second lookup to occur.
+.new
+The lookup type may optionally be followed by a comma
+and a comma-separated list of options.
+Each option is a &"name=value"& pair.
+Whether an option is meaningful depands on the lookup type.
+.wen
+
The rest of this chapter describes the different lookup types that are
available. Any of them can be used in any part of the configuration where a
lookup is permitted.
.new
.cindex "tainted data" "single-key lookups"
The file string may not be tainted
+
+.cindex "tainted data" "de-tainting"
+All single-key lookups support the option &"ret=key"&.
+If this is given and the lookup
+(either underlying implementation or cached value)
+returns data, the result is replaced with a non-tainted
+version of the lookup key.
.wen
.next
.cindex "query-style lookup" "definition of"
If set to a nonzero number of seconds, the cached value
becomes unusable after this time. Currently the dnsdb
lookup uses this to support the TTL value.
+ uschar *opts options, a comma-separated list of tagged values for
+ modifying the search operation
Even though the key is zero-terminated, the length is passed because in the
common case it has been computed already and is often needed.