[CentOS] Story of an email

Sat Nov 30 01:33:04 UTC 2013
Timothy Murphy <gayleard at eircom.net>

Mike Burger wrote:

>>>> 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.

> Assuming that you've properly configured the master.cf and main.cf to
> allow amavisd/clamav scanning of email, the following is how the process
> will flow:
> Remote mail client (user, some other mail server, etc) connects to port 25
> to send an email through your Postfix installation.
> Postfix passes the email to amavisd over some port.
> Amavisd processes the email through clamav and, if the message is clean,
> passes it back to Postfix through a different port.
> Postfix delivers the message (to a remote mail server, or to a local
> user).

Thanks for your response.
I've a couple of queries.

1) Where does SpamAssassin come into the process?

2) In my case all incoming email comes through fetchmail
from external mail servers like gmail.
I take it that this is sent through port 25 to postfix,
more precisely to the sendmail emulator of postfix?

3) I take it that in the last stage postfix passes the email to dovecot,
which stores it in ~/Maildir/cur/ (in my case).

It is picked up from there by KMail on my laptop,
but that is another story.

Timothy Murphy  
e-mail: gayleard /at/ eircom.net
School of Mathematics, Trinity College, Dublin 2, Ireland