incoming email procedure (or: mail handling route/path)

[mikesmithfl]

Hi all:
Is there a resource somewhere that describes the path that incoming email takes through all the different processing? I'm trying to get a handle on spam fighting and keep getting confused about which order the steps are followed. For instance, one question I've been wondering about: does exim use spamassassin during the processing of email acceptance or does exim finish completely with all the handling it does and then simply send the messages on to SpamAssassin (assuming SA is enabled)?
(I've tried using the search utility, but have had no good results out of LOTS of reading)

Tks,
Mike

[chirpy]

SpamAssassin with cPanel through exim is a little odd because of the way exim works:

What happens is that the email is received and processed in full but not delivered, it is then passed through exim again and processed through the SpamAssassin routers and transports (which during this second pass the email is handed to spamd and then back again) and then finally delivered to the users mailbox file.

However, if the email recipient is an alias (i.e. forwarded) and not an actual mail account, then only the first pass is done, i.e. the email is not processed through SpamAssassin, and the email relayed on.

[mikesmithfl]

That sure explains why I've been having so much trouble using SA. I hadn't known about the forwarded mail not being processed by SA. I thought I was able to just pass around individual email addresses to any of my online contacts and not worry about them, but for some reason I was getting lots of spam from some of them. I wanted to use a personalized addy at each different online store (ie bestbuy@mydomain.com) so I could keep track of which store might be responsible for passing around my email addy and then just use a SA filter for that addy if I started getting spam for it. But, I guess since I didn't actually make an email account for that address, SA wouldn't be able to stop it.

Thanks for a good detailed description!

[chirpy]

You could, of course, use MailScanner that does scan all email including forwarded email with SpamAssassin through a different method if you need that:
http://www.configserver.com/free/mailscanner.html