Weird sub-folder error

[Christian Theune]

Hi,

I’m running dovecot 2.2.13 and I ran into a weird problem.

A user migrated his mailboxes by letting users copy them from their old server to the new one through their MUA. All that went fine except for one very weird instance. The user is running Outlook 2010.

The user has a sub-folder structure which dovecot places as dotted names beneath the Inbox. (E.g. Maildir/.my.sub.folders).
After copying all data, that user came back to us and complained about missing mails in their folders. Apparently 3 of her folders disappeared.

I found folders with similar (but different!) names in the dovecot storage but with no mails in them. After a while I noticed that something made dovecot create another level of nesting, like this:

Maildir/.My.Folder/Subfolder

In this case the Original folder structure was INBOX - My - Folder - Subfolder. When the user visited the subscription settings in her MUA she found the INBOX - My - Folder mailbox which was empty. The Subfolder was nowhere to be found. This appeared weird to me. I moved the Subfolder back directly under the Maildir directory and named it “.My.Folder.Subfolder”. doveadm now lists this folder correctly.

I could not find whether this is a known bug - so I’m letting you know. Maybe you can help understand what happened. Sounds like a weird server-side bug to me - this shouldn’t happen, right?

Cheers,
Christian

—
Christian Theune · ct at flyingcircus.io · +49 345 219401 0
Flying Circus Internet Operations GmbH · http://flyingcircus.io
Forsterstraße 29 · 06112 Halle (Saale) · Deutschland
HR Stendal HRB 21169 · Geschäftsführer: Christian. Theune, Christian. Zagrodnick

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