howard.tan@gmail.com wrote:
> Hello,
>
> I'm a system administrator for a small research group. Our group has a
> lot of mail roughly 16 gigs worth for 10 users. I'm desperately trying
> to get off our Exchange 5.5 server and migrate to a
> FreeBSD/Postfix/Courier-IMAP mail server.

HI.

I would like to suggest an additional approach.
You can export all mailboxes from MS Exchange to PST files (using MS Outlook or Exmerge),
store one copy on the user PC,
and additional copy on a file server for backup.

Then you start using the new IMAP server without importing all the old emails,
and users will have access to their old emails from the PST file.

There are obvious pros and cons for such approach, but at least you should consider it.

Yizhar Hurwitz
http://yizhar.mvps.org