special_use \Archive not working with some foldernames

[Hajo Locke]

Hello list,

i use dovecot 2.2.18 compiled on my own and want to report an odd 
behaviour when using a folder for special_use \Archive. In my case it is 
not working when using some special foldernames (mbox). I compared to 
version 2.2.15 which i found pre-packaged on launchpad.net, same 
behaviour. All other special_use Folder work like expected.

My situation:
We authenticate users using mysql-db. also we allow users to store 
individuell special_use settings in db. this is a way which was 
recommended by this mailinglist some years ago.

we use a password_query like this:
password_query = SELECT `inbox` as `user`, `password`, `home` as 
userdb_home, `uid` AS userdb_uid, `gid` AS userdb_gid, `userdb_import` 
AS userdb_userdb_import FROM `mail_users` WHERE `login` = '%u' AND 
`active`='Y'

typical column in db looks like this:
| username           | cryptedpass | path | inboxname | uid | gid | 
Y      | namespace/inbox/mailbox=Sent 
namespace/inbox/mailbox/Sent/name=Gesendet 
namespace/inbox/mailbox/Sent/auto=subscribe 
namespace/inbox/mailbox/Sent/special_use=\Sent 
namespace/inbox/mailbox=Drafts 
namespace/inbox/mailbox/Drafts/name=Entwürfe 
namespace/inbox/mailbox/Drafts/auto=subscribe 
namespace/inbox/mailbox/Drafts/special_use=\Drafts 
namespace/inbox/mailbox=Trash 
namespace/inbox/mailbox/Trash/name=Papierkorb 
namespace/inbox/mailbox/Trash/auto=subscribe 
namespace/inbox/mailbox/Trash/special_use=\Trash 
namespace/inbox/mailbox=Junk namespace/inbox/mailbox/Junk/name=Spam 
namespace/inbox/mailbox/Junk/auto=subscribe 
namespace/inbox/mailbox/Junk/special_use=\Junk 
namespace/inbox/mailbox=Archives 
namespace/inbox/mailbox/Archives/name=Archiv 
namespace/inbox/mailbox/Archives/auto=subscribe 
namespace/inbox/mailbox/Archives/special_use=\Archive   |

Now i noticed that in this case the folder Archiv  was not binded to 
special_use \Archive:
* LIST (\NoInferiors \UnMarked \Junk) "/" Spam
* LIST (\NoInferiors \UnMarked \Drafts) "/" Entw&APw-rfe
* LIST (\NoInferiors \UnMarked \Sent) "/" Gesendet
* LIST (\NoInferiors \UnMarked \Trash) "/" Papierkorb
* LIST (\NoInferiors \UnMarked) "/" Archiv
* LIST (\HasNoChildren) "/" INBOX

If i change the name of folder which is binded to special_use \Archive 
its working again, no other changes:
* LIST (\NoInferiors \UnMarked \Archive) "/" Archiviu
or a shorter one:
* LIST (\HasNoChildren \Archive) "/" Arc

It works in most cases, it is not working if i have chosen name 
"Archiv". It seems also that autocreating of folder is not working if 
name is "Archiv".
I activated the debug settings but was not helpful. Looks the same in 
all cases:

Debug: Added userdb setting: namespace/inbox/mailbox=Archives
Debug: Added userdb setting: namespace/inbox/mailbox/Archives/auto=subscribe
Debug: Added userdb setting: namespace/inbox/mailbox/Archives/name=Arc
Debug: Added userdb setting: 
namespace/inbox/mailbox/Archives/special_use=\Archive

or:
Debug: Added userdb setting: namespace/inbox/mailbox=Archives
Debug: Added userdb setting: namespace/inbox/mailbox/Archives/auto=subscribe
Debug: Added userdb setting: namespace/inbox/mailbox/Archives/name=Archiviu
Debug: Added userdb setting: 
namespace/inbox/mailbox/Archives/special_use=\Archive

or the not working one:
Debug: Added userdb setting: namespace/inbox/mailbox=Archives
Debug: Added userdb setting: namespace/inbox/mailbox/Archives/auto=subscribe
Debug: Added userdb setting: namespace/inbox/mailbox/Archives/name=Archiv
Debug: Added userdb setting: 
namespace/inbox/mailbox/Archives/special_use=\Archive

I have no idea what is going wrong here.  I have no further hints in my 
logs.
What to do now? Any ideas?

Thanks,
Hajo