Software raid is installed out of the box with 7.x beta. Even if you have one drive raid 1 is installed, so you can easily add another drive. I haven't tested this yet. There has been talk about moving to postfix on the sourceforge forum, you might want to join that - smeserver.sourceforge.net. If you can help develop that, they would surely welcome the help. Or if you feel that it's necessary, then they also welcome a little cash.
Whether people think qmail is obsolete or not, it's getting the job done for now and that's all that really matters, IMO.
JB