I'm looking for a mailserver that allows a sort of whitelists.
I'm sick and tired of spam coming from so called msn.com and yahoo.com and whatnot adresses. What I would like is something that would, for example, block *@yahoo.com addresses, except "these ones".

Anyone knows anything?

Check out Merak Mail, www.merakmail.com. It has some nice options for SPAM filtering.