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@cox.net> 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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