Massive mailboxes + migration - Inviting problems?

[Chris Nolan]

Hi all!

I administer a server that runs the almighty Cyrus v2.0.16. One user has 
a total of 4.3 GB in the folders under their Inbox.

Some mail messages are apparently getting lost when sent to this person. 
Is there any sort of limit (size of messages, number of messages, number 
of folders, amount of recurssive mailboxes etc) that can cause problems? 
I've just done a reconstruct -r and am hoping for the best.

Additionally, I am looking at migrating to either the latest version of 
Cyrus or DBMail + MySQL w/ InnoDB. If I migrate to the latest version of 
Cyrus, will recreating the mailboxes, copying over the contents of the 
/var/spool/imap/user/ directories and doing a reconstruct on all of them 
do the job of getting everything ready?

If I migrate to DBMail, does anyone have any scrips to assist in this task?

For those that want to know, the current box (the one having problems), 
runs Mandrake 8.1 (Kernel 2.4.8) with ReiserFS.

Chris