Courier IMAP/POP3

WARNING: Badly done migration will cause your IMAP and/or POP3 clients to re-download all mails. Read Migration page first carefully.

Courier v0.43 and later to Dovecot v1.1+

courier-dovecot-migrate.pl does a perfect migration from Courier IMAP and POP3, preserving IMAP UIDs and POP3 UIDLs. It reads Courier's courierimapuiddb and courierpop3dsizelist files and produces dovecot-uidlist file from it.

Before doing the actual conversion you can run the script and see if it complains about any errors and such, for example:

# ./courier-dovecot-migrate.pl --to-dovecot --recursive /home
Finding maildirs under /home
/home/user/Maildir/dovecot-uidlist already exists, not overwritten
/home/user/Maildir2: No imap/pop3 uidlist files
Total: 69 mailboxes / 6 users
       0 errors
No actual conversion done, use --convert parameter

The actual conversion can be done for all users at once by running the script with --convert --recursive parameters. Make sure the conversion worked by checking that dovecot-uidlist files were created to all maildirs (including to subfolders).

The --recursive option goes through only one level down in directory hierarchies. This means that if you have some kind of a directory hashing scheme (or even domain/username/), it won't convert all of the files.

You can also convert each user as they log in for the first time, using PostLoginScripting with a script something like:

#!/bin/sh
# WARNING: Be sure to use mail_drop_priv_before_exec=yes,
# otherwise the files are created as root!

courier-dovecot-migrate.pl --quiet --to-dovecot --convert Maildir
# This is for imap, create a similar script for pop3 too
exec /usr/local/libexec/dovecot/imap

FIXME: The script should rename also folder names that aren't valid mUTF-7. Dovecot can't otherwise access such folders.

Dovecot configuration

Courier by default uses "INBOX." as the IMAP namespace for private mailboxes. If you want a transparent migration, you'll need to configure Dovecot to use a namespace with "INBOX." prefix as well.

mail_location = maildir:~/Maildir

namespace {
  prefix = INBOX.
  separator = .
  inbox = yes
}

Manual conversion

Courier's courierimapsubscribed file is compatible with Dovecot's subscriptions file, but you need to remove the "INBOX." prefixes from the mailboxes. This is true even if you set namespace prefix to "INBOX." as described above.
Courier's courierimapuiddb file is compatible with Dovecot's dovecot-uidlist file, just rename it.
Courier's message flags are compatible with Dovecot (as they are specified by the Maildir specification)
Courier's message keywords implementation isn't Dovecot compatible. There doesn't exist a simple way to convert the keywords manually.