[Dovecot] IMAP to Maildir Migration preserving UIDs?

[Gedalya]

On 01/26/2012 07:27 AM, Timo Sirainen wrote:
> 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:
>
Now, to the issue of POP3.

The old system uses the message filename for UIDL, but we need to 
migrate via IMAP in order to preserve IMAP info and UIDs (which have 
nothing to do with the POP3 UIDL in this case). So I've just finished 
writing a script to insert X-UIDL headers, and pop3_reuse_xuidl is doing 
the job.

Question: Since the system currently serves in excess of 10 pop3 
connections per second, would there be any performance gain from using 
pop3_save_uidl? Would it be faster or slower to fetch the UIDL list from 
the uidlist rather than look up the X-UIDL in the index? Just wondering.

Also, what order does dovecot return the UIDLs in?