Contact Form 7 is one of the most popular contact form plugins around. It comes ready to go right off the bat but you can always extend its capabilities with additional plugins. Message Filter for Contact Form 7 is a handy plugin that helps you get a better handle on spam submissions.
This plugin lets you decide which messages should be filtered based on certain words included in them. Admins will be able to see the latest messaged blocked, their time and associated email. They can manage restricted words and emails in the back-end.