Hi,

We just upgraded from 2.3 to 2.4.3 and are now getting errors like this for any mailbox with German umlauts in the name:

"Error: Failed to rename mailbox 'Anträge' for NFC normalization: Mailbox doesn't exist: Anträge"

The mailboxes work fine otherwise, doveadm mailbox status shows them with correct message counts. The errors show up on IMAP access but don't seem to break anything.

We're using mdbox. On disk the directory is stored as mUTF-7:

Antr&AOQ-ge

doveadm mailbox list gives back the name with c3 a4 for the ä, which is already NFC. We double-checked with python3 unicodedata and it confirms the name is NFC. So it seems like dovecot is trying to rename something that doesn't need renaming, and then failing.

Is there a way to turn off this automatic rename? Or is this a known issue with mdbox and mUTF-7 directory names?

Any help would be appreciated to find out if this is a bug or a configuration issue on our side!

Thanks, Jan