Full E-mail Setup inc spam filter - Fetchmail-Postfix-Procmail-ASK-Kmail ?

[Daniel]

Thanks Matt, Andreas, Damien and everyone, it seems I have to go back to 
the 'study bunker'.

I am feeling very ignorant, but I'm showing my ignorance rather than 
sitting in silence: I don't understand the full route of e-mail going 
through a proper system with a fully blown anti-spam script like those 
below. [still using an isp, getting the mail from them and then dealing 
with it]. I've read the general stuff, but I'm wondering if all the reading 
I'm doing is helping or digging me further in.

I am pretty keen on the anti spam solutions that will bounce spammers back 
pretending my e-mail address doesn't exist and reply to an unknown sender 
of e-mail with a password they can use if they want the mail to get 
through, like Spambouncer [Procmail only] or Active Spam Killer.  When it 
says "ASK should be invoked from .forward (or .procmailrc if you are using 
procmail). The incoming message should be piped to ASK, which will be in 
charge of doing the actual delivery."  I get the idea that it will work 
with most mail systems, and wonder if that means Maildrop (of Courier IMAP 
fame) uses .forward the same way and can thus use ASK (but not Spambouncer 
I presume as it works with .procmailrc)?

Both Spambouncer and ASK seem to use the (wanted, not wanted, and unsure) 
categories Matt referred to.

Can anyone who has time help me a bit or point me in the right direction 
please (if I don't seem like a lost cause by this time)?

My Hypothesis on How it works is as follows:


- Fetchmail goes and gets the mail [Not a mail delivery agent, but a 
remote-mail retrieval and forwarding utility - the best and the only one 
from what I can see)
- Postfix [Mail Transfer Agent] (aka E-Mail Server?).  (I'm told that 
Procmail below could do it on its own, but an MTA gives better error checking.)
- Procmail [local Mail Delivery Agent (is it Local Delivery Agent, LDA?)] 
can be made use of by Postfix to do local mail delivery.  Procmail does any 
filtering required - many scripts for fighting spam work are designed for 
Procmail.
- Kmail [Mail User Agent] lets the user read the mail etc.

(have I got the right order that the mail would travel through from start 
to finish, and what each one does?)

and the solution I like most from the little I know:

- Fetchmail
- Courier IMAP (which comes with Maildrop and uses Maildir.
- Maildrop (has standard .forward like Sendmail so mail can be passed 
through something like Active Spam Killer )[Mairdrop it says uses memory 
better than Procmail]
- Evolution [MUA]

I don't know anything about the complexity of setting up these systems, and 
wonder about that.  I think I read somewhere that Spambouncer was tough to 
set up, but wonderful to use. Mailfilter looks good and I can see good uses 
for it, but long term I would like to have the IMAP setup option.

Matt referred to another nice anti-spam setup (using procmail) from Linus
Torvald's old friend Lars Wirzenius, but although I found quite a few 
references to him, unfortunately I couldn't find the Procmail script.

Thanks - any help in getting my brain around this is greatly appreciated.
Daniel.

PS
I have read things like
(in the unlikely event there is anyone out there who is floundering like me:
http://www.windowatch.com/2001/november/linuxmail7_10.html
http://www.linuxjournal.com/article.php?sid=1196&mode=thread&order=0)