[Dovecot] IMAP to Maildir Migration preserving UIDs?

[Timo Sirainen]

On 26.1.2012, at 6.31, Gedalya wrote:

> I'm facing the need to migrate from a proprietary IMAP server to Dovecot. The migration must be as smooth and transparent as possible.
> 
> The mailbox format I would want to use is Maildir++.
> 
> The storage format used by the current server is unknown, and I don't look forward to trying to reverse-engineer it. This leaves me with the option of reading the mailboxes using IMAP. There are tools like offlineimap or mbsync, and they do store the UID and UIDVALIDITY info. The last piece of the puzzle is a process to properly create the dovecot-uidlist and dovecot-uidvalidity files. So far I wasn't able to find anything on this. Are there any tips? Are there any tools available to do this job, or part of it?

Get Dovecot v2.1 and configure it to work. Then for migration add to dovecot.conf:

imapc_host = imap.example.com
imapc_port = 993
imapc_ssl = imaps
imapc_ssl_ca_dir = /etc/ssl/certs
mail_prefetch_count = 50

And do the migration one user at a time:

doveadm -o imapc_user=USERNAME -o imapc_password=PASSWORD backup -R imapc: