Migration F8 from older release

[Luc MAIGNAN]

Hi all,

I've read at several places that upgrading Fedora 6 To F8 (even via 
temporaly an F7) is not recommended and I have to make a fresh install.

But it not possible in my mind. For exemple (I know several admin have 
the same problem), I have a mail server installed as a FC6. If I want to 
make a fresh install, I have to stop the mail server during several 
hours (install the OS, configure Postfix, spamassassin, .....) or days, 
it is not possible for my campany.

So, what is the less bad solution to upgrade my server ?

Thanks for your advices.

BR