dovecot - May 2022 - replication-/sync-problem with 'percent'-sign in foldernames after upgrade to dovecot 2.3.19

On 2022-05-17, Kurt Fitzner <kurt+dove at va1der.ca>
wrote:
> I run a medium-sized virtual domain email server for about 15 domains=2E 
I>  also use it myself and have 3 or 4 devices using imap=2E   I am often
usin> g a VPN to connect to my home network, which makes all my connections
appea> r to come from one IP=2E
>
> I want to increase mail_max_userip_connections just for myself only so
I'm>  not opening up my server to abuse=2E  Is this possible?
Simplest way is probably to add that IP to login_trusted_networks.

Hello,

after upgrading my two replicator-hosts from 2.3.18 to 2.3.19, I observe 
'failed replication'-counts with "dovecot replicator status".

The failure seems to be linked to foldernames containing a 
'percent'-sign ('%'):

"dovecot replicator status '*' | grep ' y'" now lists
some users, who
are permanently marked as 'failed'.

Trying to resync one of these users ('username') with

"doveadm -D sync -u username -d -n INBOX -l 30 -U"

stops with output:

"May 18 13:29:34
doveadm(username)<84718><TBlBD5fYhGLuSgEAZZgj0g>:
Warning: Mailbox changes caused a desync. You may want to run dsync 
again: Mailbox  AG Servicedesk/Krankmeldungen -Hiwis/krank/30%25 
mailbox_rename conflict: Can't rename mailbox to itself."

"doveadm mailbox list -u username | grep '%'" for this user
shows indeed
a folder named "AG Servicedesk/Krankmeldungen -Hiwis/krank/30%".

For the other failed users resyncing stops at equivalent foldernames 
containing a 'percent'-sign.

There are no errors or warnings noted in the logs and the replication 
for these users seems still to be working, as the total mailbox-size of 
the users is always identical on both replicators and mailbox-changes 
are noted in the logs.

Are there any ideas how to solve this?

Systemparameters are:

# 2.3.19 (b3ad6004dc): /etc/dovecot/dovecot.conf
# Pigeonhole version 0.5.19 (4eae2f79)
# OS: Linux 4.15.0-177-generic x86_64 Ubuntu 18.04.6 LTS

Mailbox-Storage is on local ZFS

Further information can be provided if needed.

With many thanks for any help,
Andreas
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