Mapping of INBOX.INBOX breaks imapc_list_prefix=INBOX?

[Timo Sirainen]

> On 06 Jan 2016, at 15:35, Timo Sirainen <tss at iki.fi> wrote:
> 
> On 06 Jan 2016, at 11:47, Peer Heinlein <p.heinlein at heinlein-support.de> wrote:
>> 
>> 
>> We're running a huge imapc-Migration from an old Courier-IMAP to Dovecot.
>> 
>> Courier always uses "INBOX."-prefix for his folders, so we set
>> 
>> namespace inbox {
>> [...]
>> separator = .
>> prefix = INBOX.
>> [...]
>> }
>> 
>> on our new Dovecot 2.2.20 system.
>> 
>> And also we added:
>> 
>> imapc_list_prefix=INBOX
>> 
>> to avoid the dublication of the INBOX prefix.
>> 
>> At the end, doveadm/dsync/imapc see "INBOX.Virus", adds his Prefix, has
>> "INBOX.INBOX.Virus", deletes his imapc_list_prefix and the end we have
>> "INBOX.Virus" again which is identical to the source folder from Courier.
>> 
>> Works perfect BUT:
>> 
>> It looks like there is a "hidden feature" in Dovecot that always maps
>> "INBOX.INBOX" back to "INBOX". For me that looks like a workaround for
>> broken mailclients to fix some of the common problems after changing the
>> namespace prefix.
>> 
>> I never heard about that "hidden feature", but even if I don't (!) have
>> INBOX.INBOX:
>> 
>> root at imap01:~/MIGRATION # doveadm mailbox list -u test
>> INBOX
>> INBOX.Virus
>> INBOX.Spam
>> INBOX.Trash
>> 
>> I'm always able to access INBOX.INBOX which is identical to INBOX:
>> 
>> root at imap01:~/MIGRATION # doveadm fetch -u test uid mailbox INBOX.INBOX
>> uid: 1
>> 
>> Looks like there is such a magic-mapping and looks like this "hard coded
>> mapping" (?) breaks the imapc_list_prefix-magic.
>> 
>> If the user has on the SOURCE-server (Courier):
>> 
>> Source-Server:
>> INBOX (5 messages)
>> INBOX.Inbox (3 messages)
>> 
>> and I do migrate that user using doveadm/dsync/imapc, this user has on
>> the DESTINATION-server (Dovecot)
>> 
>> Destination-server:
>> INBOX (5 messages)
>> INBOX.Inbox (5 messages from "real INBOX")
>> 
>> and his 3 messages from INBOX.Inbox are lost.
>> 
>> I can NOT find any errors in the debug/error-output of
>> doveadm/dsync/imapc. From the view of doveadm everything worked perfect
>> as you can see in the attached logfile.
>> 
>> Or am I completly wrong?!
> 
> It's not really a "hidden feature", but more likely a consequence of the INBOX. prefix being added/removed from folder names. I'd need to look into it more carefully to see if it's possible to fix easily or not, but I have a feeling it may not be easy. INBOX.INBOX has caused troubles many times earlier.. One solution that should work is that for dsync runs you'd simply remove the INBOX. prefix from both the namespace and the imapc_list_prefix.

Or actually that would just add INBOX. prefix to everything. Maybe removing either namespace prefix or imapc_list_prefix would work?