typo

[exim.git] / doc / doc-docbook / spec.xfpt

diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt
index cea21a18f930f85ac2e8e94a2ff827e0b9fe0a98..0385de6dbc5b96b8c907f366ce99c3b5c27604e9 100644 (file)
--- a/doc/doc-docbook/spec.xfpt
+++ b/doc/doc-docbook/spec.xfpt
@@ -32315,6 +32315,14 @@ content-scanning extension, and is available only in the DATA, MIME, and
 non-SMTP ACLs. It causes the incoming message to be scanned for a match with
 any of the regular expressions. For details, see chapter &<<CHAPexiscan>>&.
 
 non-SMTP ACLs. It causes the incoming message to be scanned for a match with
 any of the regular expressions. For details, see chapter &<<CHAPexiscan>>&.
 

+.new
+.vitem &*seen&~=&~*&<&'parameters'&>
+.cindex "&%sseen%& ACL condition"
+This condition can be used to test if a situation has been previously met,
+for example for greylisting.
+Details are given in section &<<SECTseen>>&.
+.wen
+

 .vitem &*sender_domains&~=&~*&<&'domain&~list'&>
 .cindex "&%sender_domains%& ACL condition"
 .cindex "sender" "ACL checking"
 .vitem &*sender_domains&~=&~*&<&'domain&~list'&>
 .cindex "&%sender_domains%& ACL condition"
 .cindex "sender" "ACL checking"


@@ -33039,6 +33047,59 @@ address you should specify alternate list separators for both the outer
        dnslists = <; dnsbl.example.com/<|$acl_m_addrslist
 .endd
 
        dnslists = <; dnsbl.example.com/<|$acl_m_addrslist
 .endd
 

+
+.new
+.section "Previously seen user and hosts" "SECTseen"
+.cindex "&%sseen%& ACL condition"
+.cindex greylisting
+The &%seen%& ACL condition can be used to test whether a
+situation has been previously met.
+It uses a hints database to record a timestamp against a key.
+host. The syntax of the condition is:
+.display
+&`seen =`& <&'time interval'&> &`/`& <&'options'&>
+.endd
+
+For example,
+.code
+defer  seen = -5m / key=${sender_host_address}_$local_part@$domain
+.endd
+in a RCPT ACL will implement simple greylisting.
+
+The parameters for the condition
+are an interval followed, slash-separated, by a list of options.
+The interval is taken as an offset before the current time,
+and used for the test.
+If the interval is preceded by a minus sign then the condition returns
+whether a record is found which is before the test time.
+Otherwise, the condition returns whether one is found which is since the
+test time.
+
+Options are read in order with later ones overriding earlier ones.
+
+The default key is &$sender_host_address$&.
+An explicit key can be set using a &%key=value%& option.
+
+If a &%readonly%& option is given then
+no record create or update is done.
+If a &%write%& option is given then
+a record create or update is always done.
+An update is done if the test is for &"since"&.
+
+Creates and updates are marked with the current time.
+
+Finally, a &"before"& test which succeeds, and for which the record
+is old enough, will be refreshed with a timestamp of the test time.
+This can prevent tidying of the database from removing the entry.
+The interval for this is, by default, 10 days.
+An explicit interval can be set using a
+&%refresh=value%& option.
+
+Note that &"seen"& should be added to the list of hints databases
+for maintenance if this ACL condition is used.
+.wen
+
+

 .section "Rate limiting incoming messages" "SECTratelimiting"
 .cindex "rate limiting" "client sending"
 .cindex "limiting client sending rates"
 .section "Rate limiting incoming messages" "SECTratelimiting"
 .cindex "rate limiting" "client sending"
 .cindex "limiting client sending rates"