The above message confuses users into thinking they have to do something after the installation is completed. This message should go away completely, or be replaced by one that actually checks the state of delivery (i.e. to see if procmail is the delivery agent for the mail server that is configured for use). The other part of the message, "SpamAssassin and Procmail are installed." is useful and can remain as-is.
Confusing message: "Make sure your mail server is configured to deliver using Procmail."