Re: email servers

On Fri, 2006-03-31 at 09:08 -0700, ChadDavis wrote:
Ron,

Thanks for the clear descriptions.

I have a couple of questions though.

First of all, can you confirm whether the following understanding I
now have is off target or not. I understand, now, that postfix is
both an incoming mail server and an outgoing mail server. This means
that it must listen on some port to receive email from the outside
world ( this is port 25?, SMTP ). And it means that it must listen on
some internal port, or scan some local directories, for mail to send
out to the outside world; how does this work? I think I'm confused on
the outgoing and ingoing service exposure methods. Can you please
clarify this for me?

The way I have my system configured, when I click the <Send> button,
my MUA "talks" to my MTA using a "socket". The email's bytes are
sent from the MUA to the MTA using OS+CPU+RAM. No files. Then
the MTA relays the byte stream to my ISP's smtp server.

<ron's text>
So, if you want to send emails from box to box (and, of course,
internally) on your LAN, install an MTA on each machine. They
will have to be configured so that LAN traffic stays on the LAN
and internet mail is sent to your ISP's smtp server.
</ron's text>

I'm kind of confused as to why there would be a MTA on each machine.
This probably relates to the confusion related above though. Why
couldn't I just have the one machine with postfix, which exposed its
services to the rest of my machines?

Because an MTA is how you move email from server to server, and
within the system itself.

*Remember*, all *ix boxes are servers, even if, to you, it's
a "client".

Thanks Ron,
Chad
On 3/30/06, Ron Johnson <ron.l.johnson@xxxxxxx> wrote:
On Thu, 2006-03-30 at 14:01 -0700, ChadDavis wrote:
> Hello.
>
> I'm pretty unfamiliar with email servers. I need to install
a
> server in my local network to use for development of another
> application. I just need a mail server available for the
appli-
> cation. I read some of the online documentation and became
a
> bit confused about what constitutes a server. Postfix is
on
> the system. What does it do? I don't think it has anything
to
> do with my email client, correct? My email client talks to
my
> ISP's POP server for incoming mail, and my ISP's SMTP server
for
> outgoing mail. It seems like what I need is a SMTP server
locally.
>
> Is the postfix such a thing? If not, what is an easy one
to
> install.


The MTA (Mail Transport Agent) move mail around from place to
place. Examples are:
Sendmail
qmail
postfix
exim
Exchange Server

MUA (Mail User Agent) is the client. Examples are:
Netscape Mail
Thunderbird
Outlook (Express)/Exchange
Evolution

POP (Post Office Protocol) does exactly that. It emulates
Post Office Boxes: just as the postal employee puts mail in
your PO Box, where it waits until you pick it up, so the MTA
puts mail in your "box" where it waits until your MUA fetches
it.

IMAP (Internet Mail Access Protocol) is a server-side
alternative
to storing emails on your PC. You read the email using an
MUA,
but the email stays on the server. Best for companies and
tra-
velers. Examples are:
cyrus-imap
courier-imap
dovecot-imap
uw-imap
Exchange Server

So, if you want to send emails from box to box (and, of
course,
internally) on your LAN, install an MTA on each machine. They
will have to be configured so that LAN traffic stays on the
LAN
and internet mail is sent to your ISP's smtp server.

I recommend fetchmail (a remote mail retrieval and forwarding
util-
ity) to get users' POP mail from the ISP and give it to your
MTA,
which then gives it to your IMAP server. Thus, all mail stays
on
one box, making Sarbanes-Oxley, your Auditors and your users
(when
they yell "Find that critical email I blithely deleted last
week!!"
very happy.

--
-----------------------------------------------------------------
Ron Johnson, Jr.
Jefferson, LA USA

"A man can't be too careful in the choice of his enemies."
Oscar Wilde


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Ron Johnson, Jr.
Jefferson, LA USA

"Since when do business goals (profit) come before values,
ethics, and decency?"
Dr. Laura Schlessinger
Since the time of the writing of the Old Testament...


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