I'm running postfix + dovecot on my CentOS server, together with amavisd, clamd and spamassassin, following the instructions in http://wiki.centos.org/HowTos/postfix. As far as I can see it is all working, but I must admit I'm not clear exactly what path an incoming email travels along. I asked this question before, and someone suggested a document I should read, but unfortunately I've mislaid the note I made at the time.
So if someone could enlighten me - or point to a source of enlightenment - I should be most grateful.