Yonatan -- how close is your API to being finished?
I might be able to help, although I'm still learning the differences between OpenACS 3.x and 4.x. I also don't see the acs-mail-lite package in the nightly tarball, although acs-mail is there, if only in the documentation.
I've pitched OpenACS to a number of clients lately, and I was surprised to discover that they all see Spam as a fantastic tool for sending targeting mailings to their members. I wouldn't want to have to offer them OpenACS 3.x, simply to satisfy this particular need.