diff --git a/plugins/senderbase/senderbase b/plugins/senderbase/senderbase
index 99d404cb..77a55bad 100755
--- a/plugins/senderbase/senderbase
+++ b/plugins/senderbase/senderbase
@@ -6,6 +6,14 @@
 
 senderbase - Gives the current SenderBase reputation for a mail host.
 
+SenderBase is a mail server reputation service run by Cisco.  It's
+basically a measure of how likely or unlikely they think it is for the
+server in question to be sending spam, rated on a scale of -10 (near-100%
+chance of spam) to 10 (near-0% chance of spam).  The SenderBase score for
+a server is one of several criteria that may be used when doing spam
+filtering; consequently, it's useful for the operator of a mail server to
+track their current reputation score.
+
 =head1 CONFIGURATION
 
 By default, the script will use the first IP address returned by C<hostname -I>.