[CentOS] Story of an email

[Cliff Pratt]

On Sat, Nov 30, 2013 at 2:33 PM, Timothy Murphy <gayleard at eircom.net> wrote:

> 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.
>
> Why do you insist on calling it the "sendmail emulator"? Sendmail,
postfix, exim and many others applications are merely servers that respond
to and process emails according to the SMTP protocols. There's nothing
special about sendmail except that it was one of the first and most
widespread of mail servers.

Cheers,

Cliff