[Dovecot] Moving mail servers, moving mailboxes

[Ron Leach]

On 17/04/2013 10:58, Timo Sirainen wrote:
> On 16.4.2013, at 2.48, Gregory Sloop<gregs at sloop.net>  wrote:
>
>> In short, migrating a RHEL 5.9 server running the back-ported Dovecot 1.0.7
>> To: Ububtu 12.04 with 2.0.19, I believe.
>
> Dovecot v2.0 can use v1.0's mbox/maildir files including their metadata. v2.0 should also be able to read v1.0's index files without errors.
>

We've a similar wish, except that we were hoping to install 2.2 on a 
different box (intending in our case to run Debian Squeeze instead of 
Ubuntu LTS).  Can 2.2 (or, if not, then 2.1) also read 1.0 metadata?

(Or is 'only' 2.0 able to read 1.0 metadata?  In which case we'd 
probably migrate through 2.0.x to 2.2, on Squeeze.)

Note on the Wiki:  The Migration page
http://wiki2.dovecot.org/Migration
is good at describing migration 'to' Dovecot from other systems, and 
does suggest that Dovecot will read existing files.  I think there 
were earlier discussions on the list about Dovecot version changes 
which meant that newer versions could read older versions' data, but 
older versions could not read newer versions' data.  These aspects are 
not relevant for 'migrating to' Dovecot, but are worth keeping in mind 
for 'upgrading' Dovecot.

There is version to version upgrading advice, covering all aspects, 
not only which version can read what, here
http://wiki2.dovecot.org/Upgrading

What I can see, from the descriptions of each version change, is that 
V2.x can read V1.x, but V1.2.4 or lower cannot read V2.x data.
Permissions for Maildir changed, though, in V2.0 and, then for all 
mailbox types (it says 'creating home directories', actually), in 
V2.2.  This latter change in 2.2 seems to be relevant for any 
mailboxes that will be accessed by several different users who are 
actually 'system users', ie, a mail service where the mailbox is 
'shared', and the installation is using 'system users' (not, 
therefore, using 'virtual users', if I have understood correctly).

This info is (surely) fully understood already by all the serious 
mail-server users on the list, but I wonder if it might be helpful to 
spell it out for less confident users who are getting up to speed with 
these aspects.  If the text I've written above is correct, shall I add 
it to the upgrading page of the Wiki, so that there is a definitive 
answer to the query which version(s) read what?

regards, Ron