Resolved POP3_Issue_Plesk Obsidian 18.0.73

[Jose Antonio Gil Parada]

Server operating system version

CentOS Linux release 7.9

Plesk version and microupdate number

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 included in Plesk Obsidian 18.0.73, POP3 clients began re-downloading all existing messages from the server. This behavior did not occur prior to the upgrade.

Identified Cause​

The issue has been traced to a change in the configuration parameter `pop3_uidl_format` within Dovecot. Prior to the update, the value was:

pop3_uidl_format = UID%u-%v

After the update, the default value changed to:

pop3_uidl_format = UID%{uid}-${uidvalidity}

This change in UIDL format caused POP3 clients to fail to recognize previously downloaded messages, resulting in a complete re-download.

Impact​

This behavior has affected multiple users utilizing POP3 clients, generating unnecessary traffic and confusion due to the reappearance of old emails.

Request​

We kindly request that this change in Dovecot's default configuration within Plesk Obsidian 18.0.73 be reviewed. We suggest restoring the previous value or allowing a persistent configuration that is not overwritten during future updates.

Additional Information​

Plesk Version: Obsidian 18.0.73
Dovecot Version: 2.4.1
Operating System: CentOS Linux release 7.9.2009 (Core)
Current Configuration: pop3_uidl_format = UID%{uid}-${uidvalidity}
Previous Configuration: pop3_uidl_format = UID%u-%v

We appreciate your attention and look forward to an official solution or recommendation.

Sincerely,
Jose A. Gil

 

[Sebahat.hadzhi]

Thank you for the report, @Jose Antonio Gil Parada . Our team is already working on a hotfix (PPP-69670), which should be released soon. In the meantime, the workaround our team suggests is to substitute ssl_prefer_server_ciphers = yes with ssl_server_prefer_ciphers=server and ssl_protocols with ssl_min_protocol in /etc/dovecot/conf.d/11-plesk-security-ssl.conf.

 

[Doost]

Thank you for the report, @Jose Antonio Gil Parada . Our team is already working on a hotfix (PPP-69670), which should be released soon. In the meantime, the workaround our team suggests is to substitute ssl_prefer_server_ciphers = yes with ssl_server_prefer_ciphers=server and ssl_protocols with ssl_min_protocol in /etc/dovecot/conf.d/11-plesk-security-ssl.conf.

This proposed solution doesn't apply to the issue described by the OP.
We have had clients complain of the same issue of old mails being ingested as new, unread mail by the clients' mail clients after the 18.0.73 upgrade, presumably for the same reason.

 

[AlkatraZ]

I have Dovercot not starting at all after updating Plesk (Ubuntu 24)

 

[whu]

Thank you for the report, @Jose Antonio Gil Parada . Our team is already working on a hotfix (PPP-69670), which should be released soon. In the meantime, the workaround our team suggests is to substitute ssl_prefer_server_ciphers = yes with ssl_server_prefer_ciphers=server and ssl_protocols with ssl_min_protocol in /etc/dovecot/conf.d/11-plesk-security-ssl.conf.

“When will the fix for Dovecot be available?”

 

[macadia]

Honestly, I think it's terrible that updates are released with bugs that affect the entire mail service and Plesk takes so long to release the solution as an update instead of us having to find it on the forums.

 

[Kaspar]

@Sebahat.hadzhi will this issue with the changed UID format be addressed (make it compatible with the previous format) in the upcoming update too?

 

[MSandakov]

Regarding the correct UIDL format for Dovecot 2.4, it should be configured as follows:
```
pop3_uidl_format = UID%{uid}-%{uidvalidity}
```
Unfortunately, the older format is no longer supported in this version of Dovecot. However this one should use the same variables

 

[Sebahat.hadzhi]

Apologies for the initial misunderstanding. There are quite a few issues ongoing on right now and I definitely overlooked the report.

@Kaspar as far as I am aware we do not have a registered bug for this issue.

Just to make sure I understand the issue and attempt to replicate it, and forward it for further review by our devs, could you please confirm the following:

1. You have an email account configured as POP3 in an email client (Outlook, Thunderbird, etc.)
2. After the update, old email messages that are missing from the client, but present on the server are re-imported

Are there any other steps we can perform in order to recreate the issue? Thanks in advance.

 

[LRLD]

2. After the update, old email messages that are missing from the client, but present on the server are re-imported

From what I understand, all email messages left on the server are redownloaded leading to duplicates of every email message in the client.

 

[EmilioO]

I can confirm same issue (duplication of emails) en thunderbird clients with POP3.
Be aware on dedupe emails as the size of headers its not the same..
If its helpful some clients are deduping with this tool: Remove Duplicate Messages

 

[SCRINF]

We have the same problem here after upgrading Plesk to Plesk Obsidian 18.0.73, update 1, all domains configured with POP email accounts in Outlook are receiving the emails left in copy on the server, thus creating hundreds of duplicates, the solution is urgent

 

[Sebahat.hadzhi]

@SCRINF , Plesk Obsidian 18.0.73 Update 1 should address the email re-downloading issue. Do I correctly understand that the same is still ongoing on your end after the update? If yes, could you please confirm the OS of your server?

 

[21Matze]

nano /etc/dovecot/conf.d/11-plesk-security-ssl.conf

#ssl_prefer_server_ciphers=yes

systemctl restart dovecot

Server OS Debian 12 & Ubuntu 24.04

 

[SCRINF]

AlmaLinux 9.6 (Sage Margay)
Although I believe my VPS provider has already resolved it by editing the dovecot.conf file.
I will check my inboxes again tomorrow in case it happens again.
Thanks

 

[Hangover2]

Honestly, I think it's terrible that updates are released with bugs that affect the entire mail service and Plesk takes so long to release the solution as an update instead of us having to find it on the forums.

Basically, I can only warn everyone to wait a few weeks before installing any Plesk updates on live systems.
In addition, Plesk does not mention many critical changes — such as this one — in their changelog.
You have to discover them on your own, for example by using tools to monitor configuration files. However, some changes cannot be tracked at all because they are implemented as logic inside Plesk’s encrypted PHP files.

Therefore, a safer approach is to wait first for at least #2 patch release, check the forum, deploy the update on test systems, and only then roll it out to your live environment. This workflow significantly reduces the risk of unexpected issues.

 

[JVG]

I have disabled auto updates on my Debian 12 Obsidian 18.0.72#2 server after so many reports of mail related issues with the 18.0.73 update.

This thread is marked "Resolved", I would like official confirmation that updating to 18.0.73#1 indeed solves the POP3 re-download issue (as well as the related SMTP problem and others). I cannot afford for my clients to have this problem.