We have two important WHO objects called 'Blacklist' and
'Whitelist'. Those are used in the default ruleset to globally block
-or allow specific senders.
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+or allow specific senders.
+
+WHEN - objects
+--------------
+
+image::images/screenshot/pmg-gui-mail-filter-when-objects.png[]
+
+WHEN - objects are use to activate rules at specific daytimes. You can compose
+them of one or more time-frame items.
+
+The default ruleset defines 'Office Hours', but this is not used by
+the default rules.