Re: email servers

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?

<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?

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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