If javax.activation is merely a transitive dependency for javax.mail, then it should not be explicitly declared in http://scala-tools.org/repo-releases/net/liftweb/lift/1.1-M7/lift-1.1-M7.pom

Note that according to this: http://java.sun.com/products/javamail/
the Activation framework dependency is not necessary for Java 6 users because it is included.

See thread: http://groups.google.com/group/liftweb/browse_thread/thread/f435fd3a0ddbd08e