the thing most people don't seem to realize is that this isn't a feature that all of you will be able to use on _your_ forums... in fact, i bet less than 5% of you could use it.
what you need to actually do something useful is:
correctly set up mx records for your domain
the ability to change the sendmail/postfix/whatever configs to let you pipe email
have a parser that can be run over a CLI
i'm willing to bet most of you have PHP compiled as a module, but you probably have perl installed as well..
.. so then you only need DB, mysql, mime etc. etc modules
a nicely working system like this usually costs a couple of thousand bucks (yes, this is the way most decent web-mail programs work, I've written one myself)
while i strongly disagree with anyone who think this should be released with vb3, i do think it would be a nice gesture to write up a white-paper on how it's done, but differences in different mailer-daemons makes anything beyond abstract notes unuseful
(for instance, extra headers added by sendmail aren't there in postfix & vice versa)
just my $0.02 on this subject

cool idea to use it for the forums though.. i'm impressed
[edit]
the point i'm trying to get through is that there is no way for either jelsoft or a hack-author to be able to support this, due to the vast selection of software that can/needs to be used to maintain this[/edit]