[Dovecot] FETCH got too little data (+ wrong W value) with 1 byte offset

[Vincent Artzner]

Hi there,

I juste set up dovecot as local imap server last week, with maildir format.
Things went fine with two "low volume" accounts, until I added another one.
Then I see two different things with connected clients:

1/ Quite oftent well formed messages that appear... and disappear quite
immediately.

On the server, the messages concerned by 2/ seem to be there, I can open the
files and it looks ok (header, content).

The only error log I get is this:

2011-03-18 14:43:14 IMAP(info): Info: Disconnected: FETCH failed
bytes=109363/174063195
2011-03-18 14:43:14 imap-login: Info: Login: user=<info>, method=PLAIN,
rip=192.168.0.191, lip=192.168.0.10, TLS
2011-03-18 14:43:15 IMAP(info): Error: FETCH [] for mailbox Envois UID 11572
got too little data: 63454 vs 63455
2011-03-18 14:43:15 IMAP(info): Error: Maildir filename has wrong W value:
/home/info/Maildir/.Envois/cur/1300450349.M120256P3108.Serveurlinux,S=460764,W=460768:2,S
2011-03-18 14:43:15 IMAP(info): Error: Corrupted index cache file
/home/info/Maildir/.Envois/dovecot.index.cache: Broken virtual size for mail
UID 11572

Please note the size: 63454 vs 63455: it's always like that: one byte
difference.

Here is the dovecot -n result:

# 1.2.9: /etc/dovecot/dovecot.conf
# OS: Linux 2.6.32-24-generic-pae i686 Ubuntu 10.04.2 LTS ext4
log_path: /home/dovecot.log
log_timestamp: %Y-%m-%d %H:%M:%S
listen: *:144
ssl_listen: *:10943
login_dir: /var/run/dovecot/login
login_executable: /usr/lib/dovecot/imap-login
login_process_per_connection: no
mail_max_userip_connections: 20
mail_privileged_group: mail
mail_location: maildir:/home/%u/Maildir:INBOX=/home/%u/Maildir/
mbox_write_locks: fcntl dotlock
auth default:
passdb:
driver: pam
userdb:
driver: passwd

The imap client used is thunderbird under windows XP/7. I also reproduced it
with opera mail client.
I tried to rename/delete dovecot.index.cache files as I have read about it,
but doesn't changed anything.
The incoming mails are provided to dovecot by procmail, so I think dovecot
is responsible for settings the S, W params in the filenames. No other
process should alter the messages (i still have to fully check this).

I am a bit lost (not a system administrator at all) and would be grateful
for any advice.

Vincent