I've tested this only with a test user.
http://dovecot.org/tools/courier-dovecot-migrate.pl
http://wiki.dovecot.org/Migration/Courier
# Migrate Courier IMAP (any version) and Courier POP3 (v0.43+) to Dovecot v1.0 # by Timo Sirainen. This is public domain.
# Usage: [--quiet] [--convert] [--overwrite] [--recursive] [<conversion path>] # --quiet: Print only errors # --convert: Do the actual conversion. Without this it only shows if it works. # --overwrite: Ovewrite dovecot-uidlist file even if it exists already. # --recursive: Recursively find maildirs to convert # <conversion path>: Maildir directory, or with --recursive its parent # directory or its parent's parent
# - If courierpop3dsizelist is found, it makes its best effort to keep the # POP3 UIDLs, unless the file is more than 30 days older than # courierimapuiddb (user probably stopped using POP3). # - If courierpop3dsizelist isn't found (or it's old), the dovecot-uidlist # is directly converted keeping all the UIDs. # - Keywords are converted from courierimapkeywords/ to maildir filename # flags and dovecot-keywords file # - Subscriptions from courierimapsubscribed are added to Dovecot's # subscriptions file