[Dovecot] mbox INBOX out of sync (?)

[Timo Sirainen]

On Sun, 2013-01-13 at 20:38 +0100, Tinguaro Barreno Delgado wrote:
> Hello all,
> 
> I've running a Dovecot's installation for several years without problems but since last system upgrade (Dec 26) I'm facing a kind of sync issue with the /var/mail/ inbox files.
> 
> We have got mobile and desktops IMAP clients (mostly Mozilla Thunderbird). The problem is that /var/mail/ files (mbox) aren't updated: we can delete mail from clients but they persist in de /var/mail, so the same user can see the mail again from other IMAP client.
> 
> Logs seems to be correct.

Sounds like Dovecot thinks the INBOX is read-only. What are the
filesystem permissions in the files?