After implementing bboard on top of acs-messaging, we realized that there were some performance/scalability problems with the way we were doing things. One area that hurt performance was the use of the CR; we also felt that we didn't need all the functions of the CR. Thus, we implemented acs-mail as a replacement for acs-messaging (this is discussed in the release notes somewhere, I believe). We did not remove acs-messaging so as not to break backwards-compatibility with existing applications that used acs-messaging.
