Mapping of INBOX.INBOX breaks imapc_list_prefix=INBOX?

[Peer Heinlein]

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?!

Peer




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Geschäftsführer: Peer Heinlein -- Sitz: Berlin

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