Yes, you need to cnfigure it in components.xml. You're using the email from jBoss, so you don't need to add mail.jar (already in jboss-lib). However, you need to add jboss-seam-mail.jar and depending on what you're going to do extra (things like sending attached PDF) you need to add other jars. Chapter 21 of the seam documentation explains this.
<mail:mail-session startup="true" session-jndi-name="java:/Mail" />
Thanks, Leo. That's what I needed :)