Re: [SLUG] Mail Transfer Agents

From: Paul M Foster (paulf@quillandmouse.com)
Date: Sat Nov 19 2005 - 18:51:55 EST


On Sat, Nov 19, 2005 at 06:06:46PM -0500, Sick Twist wrote:

> I am about to begin teaching myself the in's and out's of setting up a Linux
> mail server. After doing a little research, I've learned that there are a
> few different MTA's that I could use like Sendmail, Postfix, Courier, etc.
> In order to help me figure out with which one I should familiarize myself, I
> would like to hear any insight from those of you that have experience with
> this sort of thing. What are some pros and/or cons of the various MTA's?
> Which currently have good momentum in being adopted in the IT world? What is
> stable and secure?

Let the flamewars begin! ;-}

Seriously, I'm going to be baldly partisan here. Please do not take
offense; these are my opinions.

Sendmail is the most byzantine piece of software on Earth to configure.
The manual for it is huge. Much has been said about its security or lack
of same, but I don't think it's any less secure than any other MTA. It
is the oldest MTA out there. (And therefore, the cruftiest.)

Qmail is put out by a guy named Bernstein, who is both loved and hated
in the Open Source world. It appears to be a good product, but he won't
allow modifications to his source except as patches. That is, you can't
release a version of Qmail modified by you. You must ship _his_ Qmail,
and _your_ patch, if you want to do that. It is not included in Debian
for this reason.

Exim is the MTA of choice for Debian. It runs mainly as a single
program, and is not too difficult to configure, as MTAs go. I used it
for a while, but had difficulty configuring it.

Postfix is my MTA. First, it runs as a set of executables. This means
that a security hole in one may not propagate to another, unlike
programs like Exim, which run as a single executable. The paradigm for
how it runs (the interrelationship of the executables) is relatively
easy to understand. Configuration is done via a set of files in one
directory, and it is possible to actually understand (in a middling way)
how to actually configure it. It is the first MTA that I could say this
about. I still don't fully understand how it all works, but I did manage
to configure it properly for my peculiar needs.

In my opinion, configuring MTAs is hard because you must assume the
viewpoint of the computer and its relationship to your MUA and other
machines. It's hard to explain until you start getting into it. Maybe
it's just me, because I have very peculiar requirements. Also, MTAs put
a lot of attention on rewriting mail headers before the mail goes
anywhere. (Sendmail's the king of this.) It's an area I've never fully
understood.

>
> One area I would like to apply my e-mail server knowledge (once I
> aquire it) is to give my parents greater flexibility with how they can
> check their e-mail at home. They have 1 Linux box and 1 Windows box
> and there is currently no easy way for them to check the same e-mail
> account from either machine while allowing both machines to remain
> synchronized with their ISP's e-mail server. My idea is to set up an
> IMAP server on their Linux box that will automatically download mail
> from their ISP's POP3 e-mail account and serve it via IMAP to both
> computers on their LAN. Does that sound feasible?

Yep, it's possible. Just don't ask me how to do it. ;-}

Paul
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