Resolved After upgrading to 18.0.73: POP3 re-download storm due to index/UID changes (Dovecot 2.4.1)

[HoracioS]

Server operating system version

Debian 11.11

Plesk version and microupdate number

18.0.73

After updating to 18.0.73, POP3 accounts begin re-downloading all messages. Server logs show index rebuilds / changes around the upgrade window. POP3 clients treat every message as new.

What seems to be happening (technical)

• The current pop3_uidl_format uses %{uid} and ${uidvalidity}.
• If uidvalidity changes and/or indexes/uidlists are rebuilt, the server publishes different UIDLs.
• POP3 clients rely on stable UIDL; when UIDL changes, they re-fetch everything by design.

How to confirm

1. Check current Dovecot + config:
   
   dovecot --version
   doveconf -n | egrep -i 'pop3_|uidl|uidvalidity|mail_location'
   
   
2. Inspect mailbox UIDVALIDITY:
   
   doveadm mailbox status -u user@domain INBOX uidvalidity
   
   
3. Check if indexes were recreated around the upgrade:
   
   ls -l --time=ctime /var/qmail/mailnames/<domain>/<user>/Maildir/ | egrep 'dovecot\.(index|uidlist)'

Impact

• POP3 users re-download entire mailboxes (duplicates locally if clients don’t de-dupe).
• Bandwidth/storage spikes; support load increases.

I’m going to suspend Plesk updates because users are furious — and with good reason. Couldn’t Plesk have anticipated this problem beforehand?

Best regards,
Horacio Stolovitzky

 

[Doost]

Same issue as reported here:

Issue - POP3_Issue_Plesk Obsidian 18.0.73

Technical Incident Notification - Plesk Obsidian 18.0.73 Dear Plesk Support Team, Following the upgrade to Plesk Obsidian version 18.0.73, we have encountered a technical issue related to the POP3 mail service managed by Dovecot. Incident Description After updating Dovecot to version 2.4.1...

talk.plesk.com

We've had this issue affect a couple of clients (with the double-whammy of Dovecot crashing from the other issue before that), it's very frustrating.
One wonders if any testing was done at all prior to release...

 

[Sebahat.hadzhi]

The issue should be resolved after the update released yesterday - Plesk Obsidian 18.0.73 Update 1:

Fixed the issue where, after updating to Plesk Obsidian 18.0.73, the POP3 UIDL format in Dovecot was changed, causing emails to be re-downloaded (PPP-69700)

 

[CMRP]

Hello,
We have the same issue and we have find a bypass for UIDL by creating a file : /etc/dovecot/conf.d/99-local-pop3.conf
With :
protocol pop3 {
# UIDL stable recommandé (évite les re-téléchargements)
pop3_uidl_format = %{uid | hex(8)}%{uidvalidity | hex(8)}

# Optionnels mais utiles :
# Réutiliser un éventuel X-UIDL déjà présent dans les entêtes
# pop3_reuse_xuidl = yes
# En cas d’UIDL dupliqués, renommer plutôt qu’échouer
# pop3_uidl_duplicates = rename
}

We have a question : the next update 18.0.73 Update 1 will make an issue with our bypass?

 

[Sebahat.hadzhi]

@CMRP The update should not override the file /etc/dovecot/conf.d/99-local-pop3.conf, thus, your customization should remain intact. However, if I am not mistaken, your custom config will be enforced over Plesk's config, and I cannot confirm for sure whether that won't create issues in the future.

 

[CMRP]

Thank you for your response.

We know that is not the normal way but, many customers had a lot of trouble with the new update and cannot wait for an update that will arrive in several days.