The mail templating example shows that facelets templating Just Works with the Seam mail tags.
Our template.xhtml contains:
<m:message>
<m:from name="Seam" address="do-not-reply@jboss.com" />
<m:to name="#{person.firstname} #{person.lastname}">#{person.address}</m:to>
<m:subject>#{subject}</m:subject>
<m:body>
<html>
<body>
<ui:insert name="body">This is the default body, specified by the template.
</ui:insert>
</body>
</html>
</m:body>
</m:message>
Our templating.xhtml contains:
<ui:param name="subject" value="Templating with Seam Mail"/>
<ui:define name="body">
<p>This example demonstrates that you can easily use <i>facelets templating</i> in email!</p>
</ui:define>