Thanks Jan for reporting this. I also experience this Bug since having upgraded Dovecot 2.4.2 -> 2.4.3 on 2026-03-27, leading to such errors in mail.log:
Error: Failed to rename mailbox 'INBOX/Zürich' for NFC normalization: Mailbox doesn't exist: INBOX/Zürich - Zürich (in above log line) uses a decomposed sequence: a plain u (U+0075) followed by a combining diaeresis (U+0308), which the renderer stacks on top. - Zürich (which we usually type) uses a precomposed character: ü is a single code point, U+00FC (LATIN SMALL LETTER U WITH DIAERESIS). Such errors lead to broken folder structure - the user is no longer able to list the whole folder structure (except INBOX) and on mail clients like Roundcube, all folders appear as no longer subscribed. Renaming the "ü" to "ü" fixes the problem. But I have a bunch of other customers which use such characters and in previous Dovecot versions <= 2.4.2 this was never a problem. Is there any known issue / will this be addressed in the next minor version? Kind regards, Philip > On 5 May 2026, at 16:04, Jan Münnich via dovecot <[email protected]> wrote: > > Following up on my own thread in case anyone hits the same issue: > > The failed NFC rename in 2.4 left behind a duplicate mailbox with a 32-hex > GUID suffix, but only for mailboxes that had subfolders. So for every > affected name we ended up with two entries: > > Anträge > Anträge-e078d427706eda694b210000a386c91b > > The original kept its (broken) name with no message access, and the > GUID-suffixed sibling held the actual mail. Both showed up as real folders in > IMAP clients. > > I figured out from the source code that the failed rename hits a fallback > path that creates the GUID-suffixed sibling, but not what triggers the > failure in the first place. I also found a hidden option there that is not > listed in documentation, which works as a workaround to stop new occurrences: > 'mailbox_list_normalize_names_to_nfc = no'. > > Fix for already-affected mailboxes: for each one, create a temporary > ASCII-named replacement at the same hierarchy level, move the subfolders into > it, move messages from the GUID-suffixed mailbox into it, delete the > GUID-suffixed mailbox (the broken original then disappears), and rename the > replacement back to the original name. The final rename runs through the > regular code path (without NFC normalisation) and works fine. > > Kind regards, > Jan > > >> On 11 Apr 2026, at 17:25, Jan Münnich via dovecot <[email protected]> >> wrote: >> >> 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 >> >> _______________________________________________ >> dovecot mailing list -- [email protected] >> To unsubscribe send an email to [email protected] > > _______________________________________________ > dovecot mailing list -- [email protected] > To unsubscribe send an email to [email protected] _______________________________________________ dovecot mailing list -- [email protected] To unsubscribe send an email to [email protected]
