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(?) The Answer Guy (!)

By James T. Dennis, tag@lists.linuxgazette.net
LinuxCare, http://www.linuxcare.com/

(?) Installing a POP Daemon on Red Hat Linux

From Hongwei Li on Mon, 31 Jan 2000

Hi Jim,

Thank you very much! I did the following as you advised, but still failed:


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.

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?

I would greatly appreciate your help!
Hongwei Li

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.

-- He/she sent me the first advice, but didn't explain further after I asked in more detail. So, I could not do anything until I received your help.

Red Hat inexplicably puts their POP and IMAP daemons in the same file. You can install them using something like the following procedure:
1) Mount your RH Linux CD (disc #1?) using a command like:
mount /mnt/cdrom

-- I did it.

2) Go to RPM directory using something like:
cd /mnt/cdrom/Redhat/RPMS

-- then, this.

3) Install the imap....rpm package using a command like:
rpm -Uvh imap*

-- then this as:

rpm -Uvh imap-4.5.3.i386.rpm (on a RH 6.0 system)
the screen shows:
imap ##....#

... or:
rpm -i imap*
That's basically all there is to it. You can test for POP installlation/accessibility using a command like:
telnet $TARGET 110
... where $TARGET is replaced with the hostname or IP address of the system on which you hope to find a POP server.
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 /etc/hosts.deny rule between your client and the server).

-- then I try this:

telnet elyback.wustl.edu 110 from that machine (elyback) and another Linux system, but got:

 telnet: Unable to connect to remote host: Connection refused
(!) It sounds like you have a more basic networking problem. Are you sure that you have your IP addresses and routes set up correctly?

(?) Then, I reboot the machine (maybe I don't need to reboot, but enter some other command else?), try it again and still get the same message from that machine and from another system. I check the /etc/service file, it shows

 pop-3    110/tcp        # POP version 3
 pop-3    110/udp

and the /etc/hosts.deny file is empty. We don't have firewall.

(!) It's good that you checked that. Actually it's possible to put deny rules in the /etc/hosts.allow file (or vice versa). When I asked Wietse why he didn't just change that to /etc/tcpd.conf instead of having two different files who's names are obviously derived from the name of the utility that references them (/sbin/tcpd).
Remember to ensure that you have valid /etc/hosts entries for your two systems. Do a search on my FAQ or in the Linux Gazette Archives on the string:
"double reverse lookup"
... for some long explanations on why this is important.
(My first guess would be that you don't have proper /etc/hosts or DNS PTR records for these, and that your copy of TCP Wrappers may be configured (compiled) with the -DPARANOID option. Possibly that your /etc/hosts.allow has a PARANOID directive in it).

(?) So, it seems that the pop3 daemon is still not working. Is there any other way to check if it is installed and running after I did the above things?

Could you give me more advice? Thank you!

(!) The fastest way to get an answer would be to call Linuxcare's tech support number. However, that is not free. You could keep trying to get me enough information so that I could find the answer --- but I'm sure you understand that this might take a long time (I'll be gone in New York all next week, and in Arizona the week after that).
So, if you need this quickly, and are willing to pay a little bit to get some handholding consider calling 888-LIN-GURU. Otherwise I'll need to see the output from the following commands:
		script /tmp/answerguy.capture
		ifconfig -a
		route -n
		netstat -an --inet | grep LISTEN
		tail /var/log/messages
		cd /tmp
		col -b < answerguy.capture  > answerguy.txt
If you do that correctly you should see a message like: "Script done, file is /tmp/answerguy.capture" and you should find a reasonably clean copy of the the captured information in /tmp/answerguy.txt
(The 'script' or "typescript" command is what students use to capture there interactive sessions to files, so they can print their homework assignments. The col -b command "collates out" the backspaces and other control characters that might have been captured along with the text. The other commands are diagnostics and information gathering, ended by the exit command to end the typescript session).
I'd need these for both of the machines involved.
Also see if each system can "ping" the other, and try running the command:
tcpdump -n
... on the server while you are trying to access the POP service. You should be able to see the packet headers that tcpdump "sees" as the connection attempts are made.
As I say, if you decide to stick with me it could be a few weeks before I get back to you (two weeks out of town and more time to get caught up with my e-mail backup after that.
Of course you can also post this to netnews (comp.os.linux.networking) or you could subscribe to L.U.S.T. (Linux Users Support Team) which has a web page at:
L.U.S.T. Home Page:
... you can find a list of other support options at:
Netpedia Linux: Support

(!) More on: Installing a POP Daemon on Red Hat Linux

From Tim Moss on Sun, 20 Feb 2000

Tim Moss commented on one reader's apparently unresolved problem:

Have him uncomment pop-3 in his /etc/inetd.conf. I believe it is commented out by default in current Red Hat distros.

Hongwei wrote:

Hi Jim,
Thank you very much! I did the following as you advised, but still failed:
Installing a POP Daemon on Red Hat Linux

(!) Of course I should have added a "check your inetd.conf" check to my instructions.
I have mixed feelings about this change to Red Hat's default /etc/inetd.conf.
On the one hand I applaud the advance towards better security. It's long been a problem in the UNIX world that companies leave services enabled and insecurely configured in their call avoidance efforts. Doing the "right thing" can often result in getting a very large number of technical support calls, which translates to EXPENSE for the commercial software vendor.
So it's nice that Red Hat is in a business where they can fix problems like this and not worry about the consequences.
On the other hand I think that it is absurd that they haven't enhanced their RPM's and package management to resolve the issue of configuring (and re-configuring) packages as they are installed and/or after the fact.
This is one of those respects in which I prefer Debian. If I install a Debian POP server it makes sure that the inetd.conf is configured to use it. It might ask me if I want to add an entry to limit the hosts.allow that are allowed to access this service.
Of course Red Hat couldn't simply adopt the Debian strategy. The Red Hat distributions are geared for an "install everything" approach. When I try to make an initial "minimal" installation in Red Hat I find that later efforts to add packages "as needed" are frought with trips into "dependency hell."
By contrast Debian excels at the minimal installation. Later addition (and removal) of packages is more robust than I've seen under any other OS. Dependencies and conflicts are handled (mostly automatically).
(At the same time Debian has room for improvement as well. I'll save my choice comments for a review of their next major release).
(Incidentally, any reader that writes to suggest using Linuxconf will get an e-raspberry! I won't even comment on my experiences with Linuxconf. Ugh!).

Copyright © 2000, James T. Dennis
Published in The Linux Gazette Issue 51 March 2000
HTML transformation by Heather Stern of Tuxtops, Inc., http://www.tuxtops.com/

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