Flags/tags lost when moving e-mails to another folder

[Alexis Ben Miloud--Josselin]

Hi,

I have an issue with e-mail tags/flags. The IMAP user is using
Thunderbird or Roundcube with Thunderbird tags.

When the user (with an IMAP client) moves an e-mail from a
folder to another, tags set on the e-mail are lost. 

When we check the filesystem, we can see the "a" tag:

    -rw-rw---- 2 test mailusers 2498 Dec 29 15:31 'cur/1676643827.M563793P15241.<HOSTNAME>,S=2498,W=2551:2,a'

When we move the e-mail to another folder, the tag disappear:

    -rw-rw---- 2 test mailusers 2498 Dec 29 15:31 '.test/cur/1676644340.M214404P22014.<HOSTNAME>,S=2498,W=2551:2,'

In both folders, the dovecot-keywords file is:

    0 $LABEL1

The problem appeared after a major system upgrade (Debian 9 to
10). Dovecot version went from 2.2.27 to 2.3.4.1.

Some system informations:

    # dovecot --version
    2.3.4.1 (f79e8e7e4)
    # cat /etc/debian_version 
    10.13
    # uname -a
    Linux <HOSTNAME> 4.19.0-23-amd64 #1 SMP Debian 4.19.269-1 (2022-12-20) x86_64 GNU/Linux
    # findmnt /var
    TARGET SOURCE    FSTYPE OPTIONS
    /var   /dev/vda3 ext4   rw,nosuid,relatime
    # findmnt /home
    TARGET SOURCE   FSTYPE OPTIONS
    /home  /dev/vdb ext4   rw,nosuid,nodev,noexec,relatime

The output of `dovecot -n output` is here (link expires in one year):

    https://paste.evolix.org/?96d46acaea638568#56g7AQLuzJxxy4xintpexJCPgiAAG23c38irQGMkV4Rp

Here are the operations I see on an e-mail file using strace:

    15507 link("/home/test/Maildir/cur/1672326270.M619318P11927.<HOSTNAME>,S=2498,W=2551:2,Sa", "/home/test/Maildir/.test/tmp/1672326456.M737812P15507.<HOSTNAME>") = 0
    15507 rename("/home/test/Maildir/.test/tmp/1672326456.M737812P15507.<HOSTNAME>", "/home/test/Maildir/.test/cur/1672326456.M737813P15507.<HOSTNAME>,S=2498,W=2551:2,S") = 0
    15507 unlink("/home/test/Maildir/cur/1672326270.M619318P11927.<HOSTNAME>,S=2498,W=2551:2,Sa") = 0

Setting mbox_lazy_writes to yes and/or unsetting
mail_cache_fields doesn't change anything.

Any idea of what I am missing? Could this be a bug in Dovecot?

Thanks in advance,

-- 
Alexis Ben Miloud--Josselin <abenmiloud at evolix.fr>
Evolix - Hébergement et Infogérance Open Source
Marseille (37 rue Guibal, Pôle Média, 13003) / Paris / Montréal
http://evolix.com | Twitter: @Evolix @EvolixNOC | http://blog.evolix.com