[Dovecot] migrating from Courier

[LuKreme]

I've been running postfix/courier-ssl/MySQL/postfixadmin for years, but since I am in the process of building a new server I decide to reexamine my options. I'm sticking with postfix, but I've decided to move from courier to dovecot because everyone is telling me it's much faster, and I really dislike courier's SASL setup and integration with other services.

Of course, I have dozens (but not hundreds) of gigabytes of Courier Maildirs for all the users.

Most of the users are in MySQL virtual domains and their mail is stored in a common directory (/usr/local/virtual) and owned by a single system user (vpopmail). I've even hacked together a postfix service to run procmail for the virtual users, though my intention of creating a webface allowing them to muck up their own .procmailrcs never came to fruition.

I'm doing my user migration in two steps. First, I will rsync all the mail (and all the user webfiles) to the new server, do any setup/conversion/&c to the data on the new server and make sure everything is working and that passwords are preserved.

Then, right before the server goes live I will shutdown mail on the old machine, rsync any new mail (hopefully no more than a couple of hours worth) over, do any conversion, and then fire up the new server.

1) what do I need to do to convert or prepare the courier maildirs for dovecot?

2) is the current setup of virtual users reasonable for dovecot?
  2.1) Is there a better option than postfixadmin?

3) some of my users are not in MySQL, but are real system users. Is this going to confuse dovecot (it confuses courier no end). These system users are still using courier and courier maildirs.

4) would it be better to take the server live and THEN move/convert the old mail?

5) anything else obvious that I didn't mention or ask that I should have?

The most important thing, of course, is to not lose anyone's email.

-- 
"Two years from now, spam will be solved," -- Bill Gates, January,
	2004