# - prefix: name (default: "")
# prefix to the name of the greylist database
# - lookup_by_host: boolean (default: false)
-# perform lookup per host instead of domain.
+# perform lookup per host. The default behaviour is to remove the last number of the IP
+# to match a domain. This behaviour is disabled if a part of the IP is contained in the
+# hostname (look like a dialup ip from a provider). With this flag on, the "domain"
+# matching is always disable.
+# - no_sender: boolean (default: false)
+# do not use the sender address. Default behaviour is to greylist using the tuple
+# (client_address, sender, recipient). With this flag on, the sender is not used.
+# - no_recipient: boolean (default: false)
+# same as no_sender but with recipient.
# - delay: number (default: 300)
# number of seconds the client must wait before retrial.
# - retry_window: (default: 2 * 24 * 3600)
# - if the client is greylisted, returns greylist
# - if a error occured (not currently possible), returns error
# State:
-# this filter is a recipient filter and works in RCPT state only
-# (smtpd_recipient_restrictions).
+# this filter is a recipient filter and works in RCPT state onl if no_recipient
+# is not specified (smtpd_recipient_restrictions). If no_sender is not given, this
+# requires a sender name, and so must be called after MAIL TO.
# Perform greylisting
greylist {