116 lines
5.1 KiB
HTML
116 lines
5.1 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
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<HTML>
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<HEAD>
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<META NAME="GENERATOR" CONTENT="SGML-Tools 1.0.9">
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<TITLE>The Linux Electronic Mail Administrator HOWTO: Choosing a Mail Transport Agent</TITLE>
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<LINK HREF="Mail-Administrator-HOWTO-6.html" REL=next>
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<LINK HREF="Mail-Administrator-HOWTO-4.html" REL=previous>
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<LINK HREF="Mail-Administrator-HOWTO.html#toc5" REL=contents>
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</HEAD>
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<BODY>
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<A HREF="Mail-Administrator-HOWTO-6.html">Next</A>
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<A HREF="Mail-Administrator-HOWTO-4.html">Previous</A>
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<A HREF="Mail-Administrator-HOWTO.html#toc5">Contents</A>
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<HR>
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<H2><A NAME="s5">5. Choosing a Mail Transport Agent</A></H2>
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<P>Mail transport agents are the software that transfers mail from your
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local system to remote systems. It is very seldom necessary to mess
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with or replace your MTA on a modern Linux, and you're better off not
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fixing what isn't broken. Nevertheless, here's a survey to get you
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started on understanding what the tradeoffs are if you decide you need
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more security or performance than your system's default can offer.
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<P>(There are other Unix MTAs besides these, but you are quite unlikely
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to encounter them on a Linux box.)
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<P>Each has its own unique features, but the best compromise is qmail. It
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features high security (even if vmail is more secure), high speed
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(even if smail is faster for local uses) and ease of configuration.
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Of course, feel free to choose any mail software. The information
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provided here is intended to help you choose well.
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<P>Sendmail can be nice for many sites with complicated options, but I think its
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configuration is too hard for beginners while it is not very secure or very
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fast, so there is only a <B>really</B> outdated sendmail section in this HOWTO.
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<P>If you know what you're doing, choose sendmail (and you shouldn't be
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reading this HOWTO!); otherwise I generally recommend qmail.
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<P>Detailed descriptions of these programs follow.
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<P>
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<H2><A NAME="ss5.1">5.1 sendmail</A>
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</H2>
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<P>BSD sendmail is the grandaddy of Internet MTAs. It has outlasted a few
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would-be successors. Most Linux distributions now use it and have it
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preinstalled.
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<P>
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<P>Sendmail has a long-standing reputation for being an administrator's
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nightmare -- hard to understand, tricky to configure, rife with
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security holes. As Internet technology and standards have stabilized,
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however, many of the sendmail options and configurable rules that gave
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rise to this reputation have ceased to require per-site tweaking
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(the effective demise of non-TCP/IP network layers like UUCP has
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helped a lot). Also, recent sendmail versions have an improved
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configuration system that insulates you from the legendary hideousness
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of the sendmail.cf configuration file. Most importantly, sendmail now
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normally comes preconfigured, and you should never need to touch it
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unless you have unusual requirements (such as needing to route mail
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over a non-TCP/IP network).
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<P>
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<P>There is a sendmail home page at
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<A HREF="http://www.sendmail.org">http://www.sendmail.org</A>.
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It includes references to extensive documentation of sendmail, should
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you actually need to wrestle with custom-configuring it.
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<P>
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<P>Other MTAs, if called as `sendmail', may mimic the semantics of
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sendmail's command-line options. This is convenient for mail user
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agents, which often assume they are talking to sendmail.
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<P>
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<P>
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<H2><A NAME="ss5.2">5.2 smail v3.2</A>
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</H2>
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<P>Smail was the first serious attempt to replace sendmail. It has a
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simpler and much more comprehensible configuration system than
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sendmail's, and it's fairly secure. Some Linux distributions
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preinstall it rather than sendmail.
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<P>
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<P>At one time smail's excellent support for mixed TCP/IP and UUCP sites
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was a major selling point for it, but as UUCP has declined, so has
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smail. Also, smail is less efficient than sendmail on high-volume
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connections.
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<P>
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<P>As with sendmail, it is unlikely that you will need to tweak a
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preinstalled smail configuration.
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<P>
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<P>(Very occasionally you might run across references to an `smail 2.5'.
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This program has been obsolete for a long time. Don't bother with it.)
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<P>
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<H2><A NAME="ss5.3">5.3 qmail</A>
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</H2>
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<P>The qmail program is a sendmail-compatible MTA designed specifically
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for high security. The author has a standing reward of $500 for
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publication of the first verifiable security hole; this reward has gone
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unclaimed since March 1997.
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<P>The qmail home page is at
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<A HREF=" http://pobox.com/~djb/qmail.html"> http://pobox.com/~djb/qmail.html</A>.
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<P>
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<H2><A NAME="ss5.4">5.4 exim</A>
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</H2>
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<P>The exim program is similar to smail3, but with more features. It
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advertises particular strengths in spam-blocking and support of several
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virtual hosts (virtual DNS domains) on the same host.
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<P>The exim home page is at
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<A HREF=" http://www.exim.org/"> http://www.exim.org/</A>.
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<P>I tried it on my own computer, it looks like a nice merge between
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smail configuration system and qmail security, moreover it has the
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advantage of being GPL.
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<P>A section explaining how to replace your current MTA by exim will be
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added soon.
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<P>
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<HR>
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<A HREF="Mail-Administrator-HOWTO-6.html">Next</A>
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<A HREF="Mail-Administrator-HOWTO-4.html">Previous</A>
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<A HREF="Mail-Administrator-HOWTO.html#toc5">Contents</A>
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