Configuring Your POP Mail Server
Each user on your Linux box will get mail sent to their account's mail folder, but sendmail just handles mail sent to your my-web-site.org domain. If you want to retrieve the mail from your Linux box's user account using a mail client such as Evolution, Microsoft Outlook or Outlook Express, then you have a few more steps. You'll also have to make your Linux box a POP mail server.
Fedora Linux comes with its Cyrus IMAP/POP server RPM package, but I have found the IMAP-2002 RPMs found on rpmfind.net and featured in this section much more intuitive to use for the SOHO environment.
Installing Your POP Mail Server
You need to install the imap RPM that contains the POP server software. It isn't yet a part of the Fedora RPM set, and you will probably have to download it from rpmfind.net. Remember that the filename is probably similar to imap-2002d-3.i386.rpm.
Starting Your POP Mail Server
POP mail is started by xinetd. To configure POP mail to start at boot, therefore, you have to use the chkconfig command to make sure xinetd starts up on booting. As with all xinetd-controlled programs, the chkconfig command also immediately activates application.
[root@bigboy tmp]# chkconfig pop3 on
To stop POP mail after booting, once again use chkconfig:
[root@bigboy tmp]# chkconfig pop3 off
Remember to restart the POP mail process every time you make a change to the configuration files to ensure the changes take effect on the running process.
How to Configure Your Windows Mail Programs
All your POP e-mail accounts are really only regular Linux user accounts in which sendmail has deposited mail. You can now configure your e-mail client such as Outlook Express to use your new POP/SMTP mail server quite easily. To configure POP Mail, set your POP mail server to be the IP address of your Linux mail server. Use your Linux user username and password when prompted.
Next, set your SMTP mail server to be the IP address/domain name of your Linux mail server.
Configuring Secure POP Mail
If you need to access your e-mail from the mail server via the Internet or some other insecure location, you may want to configure POP to work over an encrypted data channel. For this, use /etc/xinetd.d/pop3s file instead of /etc/xinetd.d/ipop3. Encrypted POP runs on TCP port 995, so firewall rules may need to be altered as well.
Most POP clients support secure POP. For example, Windows configures it in the Advanced menu of the Outlook Express Account Configuration window.
How to Handle Overlapping E-mail Addresses
If you have user overlap, such as John Smith (john@my-web-site.org) and John Brown (john@another-web-site.org), both users will get sent to the Linux user account john by default. You have two options for a solution:
Make the user part of the e-mail address differentjohn1@my-web-site.org and john2@another-web-site.org, for exampleand create Linux accounts john1 and john2. If the users insist on overlapping names, then you may need to modify your virtusertable file. Create the user accounts john1 and john2 and point virtusertable entries for john@my-web-site.org to account john1 and point john@another-web-site.org enTRies to account john2. The POP configuration in Outlook Express for each user should retrieve their mail via POP using john1 and john2, respectively. With this trick you'll be able to handle many users belonging to multiple domains without many address overlap problems.
Troubleshooting POP Mail
The very first troubleshooting step is to determine whether your POP server is accessible on the POP TCP port 110 or the secure POP port of 995. Lack of connectivity could be caused by a firewall with incorrect permit, NAT, or port forwarding rules to your server. Failure could also be caused by the xinetd process being stopped or the configuration files being disabled. Test this from both inside your network and from the Internet. (Troubleshooting TCP with TELNET is covered in Chapter 4.)
Linux status messages are logged to the file /var/log/messages. Use it to make sure all your files are loaded when you start xinetd. Check your configuration files if it fails to do so. This example starts xinetd and makes a successful secure POP query from a remote POP client. (Linux logging is covered in Chapter 5, "Troubleshooting with syslog.")
Aug 11 23:20:33 bigboy xinetd[18690]: START: pop3s pid=18693
from=172.16.1.103
Aug 11 23:20:33 bigboy ipop3d[18693]: pop3s SSL service init from
172.16.1.103
Aug 11 23:20:40 bigboy ipop3d[18693]: Login user=labmanager host=172-
16-1-103.my-web-site.org [172.16.1.103] nmsgs=0/0
Aug 11 23:20:40 bigboy ipop3d[18693]: Logout user=labmanager host=172-
16-1-103.my-web-site.org [172.16.1.103] nmsgs=0 ndele=0
Aug 11 23:20:40 bigboy xinetd[18690]: EXIT: pop3s pid=18693
duration=7(sec)
Aug 11 23:20:52 bigboy xinetd[18690]: START: pop3s pid=18694
from=172.16.1.103
Aug 11 23:20:52 bigboy ipop3d[18694]: pop3s SSL service init from
172.16.1.103
Aug 11 23:20:52 bigboy ipop3d[18694]: Login user=labmanager host=172-
16-1-103.my-web-site.org [172.16.1.103] nmsgs=0/0
Aug 11 23:20:52 bigboy ipop3d[18694]: Logout user=labmanager host=172-
16-1-103.my-web-site.org [172.16.1.103] nmsgs=0 ndele=0
Aug 11 23:20:52 bigboy xinetd[18690]: EXIT: pop3s pid=18694
duration=0(sec)
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