Instead of PyLucene I would suggest Xapian (http://www.xapian.org). The indexer library is written in C++, is damn fast, scales well and has nice Python bindings. I have written a small desktop search app in only one evening.
The email package is very helpfull for parsing mail but you still have a lot of stuff to do. See http://www.strakt.com/docs/ep04_email.pdf (Real-world email handling in python).
I just tried Xapian out -- builds easily, looks like fairly straight-forward Python bindings, and okay documentation. Very interesting. PyLucene still drives me nuts to build, so it's just not worth pursuing at the moment, and I'm not even sure if it offers anything over Xapian. I'd looked at Swish-E quite a bit before, but Xapian looks a little more modern and with better-defined layers.