If your long term aim is to use Qmail then now might be the time to do it. If you have the convert-and-create script then you should be able to convert to Qmail in about 2 hours (this is assuming that you have no previous experience with Qmail). The last system I converted to Qmail took a total of 45 minutes, and that included fixing a number of accounts that had missing home directories or home directories with the wrong ownership/permissions.

1. Install the binaries and update the inetd.conf file for tcp-env and qmail-popup.
2. Setup the /etc/qmail files and the ~alias files for postmaster and root and any other impotant aliases. Don't use an /etc/qmail/rcpthosts file initially - it'll make things unnecessarily difficult.
3. Create a .qmail file for each user with the contents "./Maildir/" and make it owned by the user with permissions 1600 (the tag bit stops delivery). At this time your old Sendmail/Smail setup is still functioning normally.
4. Do a trial run of convert-and-create, if it gives any errors then remove all the Maildir's and run it again. When you get it going with no errors then remove the Maildir's in preparation for the real run. Every time I've done this I've found dozens of errors and taken a few attempts to get it right.
5. Put the appropriate entries in your inetd.conf or xinetd.conf file for the tcp-env and qmail-popup services - these won't take affect until you "kill -1" the inetd server.
6. Kill the sendmail and cucipop daemons. Now you have no functional mail server so it's not the time for a lunch break. ;)
• Run convert-and-create - you've tested this so it'll run straight through. Assuming that you have a few hundred megs of email it'll take a few minutes to run, but don't worry - continue working with this process in the background or on another VT.
• Kill -1 the inetd process to start the qmail SMTP and POP servers. For the next few minutes most of the accounts won't have Maildir's, but that's OK. Qmail will just spool mail to be delivered to those accounts because of the tag bit. The POP server won't be fully operational for a while - but you can live without it for a few minutes.
• Search through the users home dirs for .forward or .procmail files and do appropriate similar things in the new .qmail files. If some of these files are overly complex then just leave the tag bit on the user's .qmail file and you can get back to it later.
• When convert-and-create is finished chmod all the .qmail files to mode 0600 except for any special cases from due to .forward files or .procmail files.
• Send a SIGALRM to the qmail-send process to hurry through delivery of spooled mail (this is optional - it just makes things a bit quicker).
9. Now everything is working fine for the regular users (those who don't use .forward files, elm, or pine - IE the POP/SMTP users). So you can spend some time writing bulletins about the changes for those who have shell accounts.