After reading extensively through the many threads and pulling out what little hair I have left, I have finally figured out how to setup VirtualMin in a "Windoze" environment to minimally impact users.
There are essentially six things to do:
1) Do a clean, fresh install of the OS (CentOS 5.4) in my case, make sure you set the "hostname" to something that is NOT going to be one of the domains hosted on VirtualMin.
2) Install VirtualMin from the "install.sh" script. After it is done installing, reboot and then "update" all the system packages from within VirtualMin.
3) in "/etc/sysconfig/saslauthd" edit the "FLAGS=" to read "FLAGS=-r" . You can use the "File Manager" on the "Webmin" side under the "Others" link and "File Manager" . Just navigate to the file and use the "edit" icon on the toolbar to edit and save the changes to "saslauthd".
4) now click on the "Servers" link and then click on the "Dovecot" link. You will see the "Edit Config FIle" icon to the right. Click on it. Scroll down until you see "#disable_plaintext_auth = no". Remove the "#" to uncomment this line. Click on the "Save" button.
5) now click back over to the VirtualMin side. Click on "System Settings ->Server Templates->Default Settings" From the drop down menu, select "Mail for Domain". Scroll to the bottom. From the very last line that says "Format for usernames that include domain" select "username@domain" from the drop down menu. Click on "Save" button. Reboot the system.
6) in Outlook Express, setup the user email account as normal. When done, bring up the Account->Properties->Server tab and make sure to tick the box that says "My servers requires authentication" Click on OK.
You are done! You should now be able to send and receive email normally (or for what passes as normal in a "Windoze" environment.
Make sure when the user refreshes his IMAP folders list, that they also "subscribe" (double click on the "spam" folder. Otherwise, stuff that SpamAssassin culls into this folder won't be seen by the user. Set up this folder to synchronize along with the InBox so the users can see when messages arrive.
Hope this helps.... Also thanks to the authors of WebMin and VirtualMin. Good job folks. As a suggestion, you may want to give the above configuration items consideration when modifying your install script so as to help out poor helpless noobs like me... thanks again.
--David LeNorman..