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<TITLE>The Answer Guy 50: Installing a POP Daemon on Red Hat Linux</TITLE>
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<H4>"The Linux Gazette...<I>making Linux just a little more fun!</I>"</H4>
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<H4>By James T. Dennis,
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<!-- begin 48 -->
<H3 align="left"><img src="../../gx/dennis/qbubble.gif"
height="50" width="60" alt="(?) " border="0"
>Installing a POP Daemon on Red Hat Linux</H3>
<p><strong>From Hongwei Li on Sat, 22 Jan 2000
</strong></p>
<!-- ::
Installing a POP Daemon on <A HREF="http://www.redhat.com/">Red Hat</A> Linux
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
:: -->
<P><STRONG>
Hi,
</STRONG></P>
<P><STRONG>
I recently installed RedHat 6.0 and 6.1 on two machines,
respectively. Everything looks working except that users can not
access their e-mail accounts on these two servers from PC Windows
using Netscape Mail or MS Outlook Express although they can access
the e-mails using telnet, pine. Apparently, POP3 daemon is not
working on these two RH Linux boxes.
</STRONG></P>
<P><STRONG>
Somebody said I can retrieve POP3 daemon from IMAP package. But,
I don't know where it is and how to do it. Could you help me?
How to check the system if POP3 daemon is installed and working?
Where can I get IMAP package and retrieve POP3 daemon, then
installed it and let it run? or should I get something else?
</STRONG></P>
<P><STRONG>
I would greatly appreciate your help!
</STRONG></P>
<P><STRONG>
Hongwei Li
</STRONG></P>
<BLOCKQUOTE><IMG SRC="../../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
Your "somebody" is a smart cookie. You sould listen
to him or her. However, you might ask him (or her) for
a wee bit more detail.
</BLOCKQUOTE>
<BLOCKQUOTE>
Red Hat inexplicably puts their POP and IMAP daemons
in the same file. You can install them using
something like the following procedure:
</BLOCKQUOTE>
<BLOCKQUOTE>
1) Mount your RH Linux CD (disc #1?) using
a command like:
</BLOCKQUOTE>
<BLOCKQUOTE><BlockQuote><Code>
mount /mnt/cdrom
</Code></BlockQuote></BLOCKQUOTE>
<BLOCKQUOTE>
2) Go to RPM directory using something like:
</BLOCKQUOTE>
<BLOCKQUOTE><BlockQuote><Code>
cd /mnt/cdrom/Redhat/RPMS
</Code></BlockQuote></BLOCKQUOTE>
<BLOCKQUOTE>
3) Install the imap....rpm package using a
command like:
</BLOCKQUOTE>
<BLOCKQUOTE><BLOCKQUOTE><CODE>
rpm -Uvh imap*
</CODE></BLOCKQUOTE></BLOCKQUOTE>
<BLOCKQUOTE>
... or:
</BLOCKQUOTE>
<BLOCKQUOTE><BLOCKQUOTE><CODE>
rpm -i imap*
</CODE></BLOCKQUOTE></BLOCKQUOTE>
<BLOCKQUOTE>
That's basically all there is to it. You can
test for POP installlation/accessibility using a
command like:
</BLOCKQUOTE>
<BLOCKQUOTE><BlockQuote><Code>
telnet $TARGET 110
</Code></BlockQuote></BLOCKQUOTE>
<BLOCKQUOTE>
... where $TARGET is replaced with the hostname or
IP address of the system on which you hope to find
a POP server.
</BLOCKQUOTE>
<BLOCKQUOTE>
If you get a "connection refused" or a "connection
closed by remote host" then you don't have POP installed
properly on the $TARGET system (or you have a firewall,
packet filter, or <TT>/etc/hosts.deny</TT> rule between your client
and the server).
</BLOCKQUOTE>
<BLOCKQUOTE>
Otherwise you should get something a little like this:
</BLOCKQUOTE>
<blockquote><pre>Trying 123.45.67.8...
Connected to popserver.wherever.not.
Escape character is '^]'.
+OK <13260.948530011@popserver.wherever.not>
USER nobody
+OK
PASS somedumbpassword
+OK Mailbox open, 4294967295 messages
QUIT
</pre></blockquote>
<BLOCKQUOTE>
The USER, PASS and QUIT commands were typed by me. There
are additional POP 3 protocol commands you could use to play
with the server manually, but this is enough to verify that
the server is running, that the user name and password are
valid and that the POP server isn't having trouble opening
the user's mail spool.
</BLOCKQUOTE>
<BLOCKQUOTE>
NOTE: The PASS command is simply transmitting and
displaying your password. Don't do this over an insecure
network or with a bad person looking over your shoulder!
</BLOCKQUOTE>
<BLOCKQUOTE>
(Also note: The number of messages that the POP daemon
reports as being in your inbox had better be alot less
then what I show in this example: 2^32 - 1).
</BLOCKQUOTE>
<BLOCKQUOTE>
As for you question about whether you should get something
else (something other than the POP daemon that Red Hat
packages in their IMAP RPM file): That's entirely up to you.
</BLOCKQUOTE>
<BLOCKQUOTE>
I did dig up a page where Cameron Laird started
collecting notes for a comparison of POP daemons
(<A HREF="http://starbase.neosoft.com/~claird/comp.mail.misc/POP_comparison.html"
>http://starbase.neosoft.com/~claird/comp.mail.misc/POP_comparison.html</A>)
</BLOCKQUOTE>
<BLOCKQUOTE>
It doesn't offer much commentary nor comparison, yet.
However, it does offer links to over a dozen POP servers.
Surprisingly I couldn't find any other online articles
that offer a comparison or summary of POP daemons and
server.
</BLOCKQUOTE>
<BLOCKQUOTE>
One of the most popular POP daemons is QPopper
(<A HREF="http://www.eudora.com/freeware/qpop.html"
>http://www.eudora.com/freeware/qpop.html</A>). This is
a (relatively) free package from the publishers of
the Eudora mail client software for Macs and MS Windows.
One of the principle advantages of this package is
its support for changing passwords through it's own
client/server protocol. To enable this you have to
install the poppasswd daemon in addition to the
qpopper daemon.
</BLOCKQUOTE>
<BLOCKQUOTE>
If you replace your MTA (mail transport agent) with
qmail then you'll want to switch to the qmail-pop3d
daemon (which comes with qmail). You can find out more
than you wanted to know about that and many addons,
and optional packages and patches related to it by
searching the Qmail home page (<A HREF="http://www.qmail.org"
>http://www.qmail.org</A>)
on the term "POP."
</BLOCKQUOTE>
<BLOCKQUOTE>
It's a pity there isn't more info to guide users
in selecting a POP daemon. Then again, basic POP
is a pretty protocol with only a very focussed purpose.
Any of them should do the basic job at hand.
</BLOCKQUOTE>
<BLOCKQUOTE>
If you're allowing POP from outside of your network
(beyond your organization's firewall or packet filters)
then you should require APOP authentication or you should
ensure that your outside clients are connecting through
a secure channel (like <A HREF="http://www.xs4all.nl/~freeswan/">FreeS/WAN</A> <A HREF="http://www.xs4all.nl/~freeswan"
>http://www.xs4all.nl/~freeswan</A>
or an ssh tunnel).
</BLOCKQUOTE>
<BLOCKQUOTE>
APOP is an extension to the POP protocol that uses a
challenge-response exchange to perform the authentication
(there's also a KPOP variation for sites using Kerberos).
What is remarkable is that I don't see options in any of
the software that I've looked at to DISABLE plain text
passwords (so that you can enforce a policy that your
external users MUST use APOP).
</BLOCKQUOTE>
<BLOCKQUOTE>
It doesn't sound like this will be a problem for you,
but if it is (and for the benefit of my other readers)
here's a couple of links to information about POP over
ssh, and how to configure a system to allow POP and/or
IMAP over SSL (secure socket layer).
</BLOCKQUOTE>
<BLOCKQUOTE><DL><DT>
Secure POP via SSH mini-HOWTO
<DD><A HREF="http://www.linuxdoc.org/HOWTO/mini/Secure-POP%2BSSH.html"
>http://www.linuxdoc.org/HOWTO/mini/Secure-POP%2BSSH.html</A>
<dt>
linuxsec: [linux-security] Re: POP secure access??
<dd><A HREF="http://www-uxsup.csx.cam.ac.uk/lists/linuxsec/0104.html"
>http://www-uxsup.csx.cam.ac.uk/lists/linuxsec/0104.html</A>
</DL></BLOCKQUOTE>
<BLOCKQUOTE>
Hope all that helps.
</BLOCKQUOTE>
<!-- sig -->
<!-- end 48 -->
<hr width="40%" align="center">
<!-- begin 2 -->
<H3 align="left"><img src="../../gx/dennis/qbubble.gif"
height="50" width="60" alt="(?) " border="0"
>IMAP/POP daemon on RH 6.0 and 6.1</H3>
<p><strong>From Randall Gellens on Sun, 30 Jan 2000
</strong></p>
<P><STRONG><FONT COLOR="#000066"><EM>
One of the most popular POP daemons is QPopper
(<A HREF="http://www.eudora.com/freeware/qpop.html"
>http://www.eudora.com/freeware/qpop.html</A>). This is
a (relatively) free package from the publishers of
the Eudora mail client software for Macs and MS Windows.
</EM></FONT></STRONG></P>
<P><STRONG>
Why do you say "relatively"?
</STRONG></P>
<BLOCKQUOTE><IMG SRC="../../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
I was under the misconception that Qualcomm was imposing
some restrictions on the distribution of qpopper
derivatives. However, I copied you so that you could
clear that up for me. (I see that it's not listed
as "non-free" by my <A HREF="http://www.debian.org/">Debian</A> package lister and now
I see that it appears to be a BSDish license.
</BLOCKQUOTE>
<BLOCKQUOTE>
So, I was wrong to qualify it this way. Qpopper is a
free package.
</BLOCKQUOTE>
<P><STRONG><FONT COLOR="#000066"><EM><IMG SRC="../../gx/dennis/qbub.gif" ALT="(?)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
If you replace your MTA (mail transport agent) with
qmail then you'll want to switch to the qmail-pop3d
daemon (which comes with qmail). You can find out more
than you wanted to know about that and many addons,
and optional packages and patches related to it by
searching the Qmail home page (<A HREF="http://www.qmail.org"
>http://www.qmail.org</A>)
on the term "POP."
</EM></FONT></STRONG></P>
<P><STRONG>
Many people use Qpopper and Qmail together. There is a <TT>./configure</TT>
option for Qpopper to use Qmail's home dir mail spool.
</STRONG></P>
<BLOCKQUOTE><IMG SRC="../../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
Glad to hear it. I obviously haven't been using qpopper
recently. I should probably switch.
</BLOCKQUOTE>
<P><STRONG><FONT COLOR="#000066"><EM><IMG SRC="../../gx/dennis/qbub.gif" ALT="(?)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
APOP is an extension to the POP protocol that uses a
challenge-response exchange to perform the authentication
(there's also a KPOP variation for sites using Kerberos).
What is remarkable is that I don't see options in any of
the software that I've looked at to DISABLE plain text
passwords (so that you can enforce a policy that your
external users MUST use APOP).
</EM></FONT></STRONG></P>
<P><STRONG>
By default, Qpopper does not permit users to log in with plain text
passwords if they are enabled for APOP (or SCRAM).
</STRONG></P>
<BLOCKQUOTE><IMG SRC="../../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
Maybe the FAQ or README should clarify that. Maybe
I missed it. That's one of the reasons that I try to
copy the "right" people when I'm doing my "Answer Guy"
responses. I learn from my mistakes that way.
</BLOCKQUOTE>
<BLOCKQUOTE>
Is SCRAM some variant of the CRAM-MD5? (challenge/response
authentication mechanism: RFC 2095 and 2195?)
</BLOCKQUOTE>
<BLOCKQUOTE>
Does that get around the need to store the POP user's
cleartext password on the server? I read through these
RFCs and didn't quite get the part about storing
"contexts" rather than copies of the cleartext passwords.
(I didn't spend long on it, but I think I'm missing
some detail here --- I should probably read some source
code to an implementation to see what I missed).
</BLOCKQUOTE>
<P><STRONG><IMG SRC="../../gx/dennis/qbub.gif" ALT="(?)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
Randall Gellens
<em><br>Opinions are personal; facts are suspect; I speak for myself only
<br>--- randomly selected quote ---
<br>A child of five would understand this. Send somebody to
fetch a child of five. --Groucho Marx, _Duck Soup_
</em></STRONG></P>
<!-- sig -->
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<!--startcut ======================================================= -->
<P> <hr> <P>
<H5 align="center"><a href="http://www.linuxgazette.com/copying.html"
>Copyright ©</a> 2000, James T. Dennis
<BR>Published in <I>The Linux Gazette</I> Issue 50 February 2000</H5>
<H6 ALIGN="center">HTML transformation by
<A HREF="mailto:star@starshine.org">Heather Stern</a> of
Starshine Technical Services,
<A HREF="http://www.starshine.org/">http://www.starshine.org/</A>
</H6>
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