Bug 502976

SUMMARY
Kmail2 randomly redownloads some emails over and over again via POP3 if you want to keep some emails on the server.

STEPS TO REPRODUCE
1. Configure a POP3 account keeping the emails from the last, say 30 days on the server
2. Download the emails regularly
3. 

OBSERVED RESULT
After a while, already downloaded emails are downloaded again

EXPECTED RESULT
Already donwloaded emails should not be downloaded again

SOFTWARE/OS VERSIONS
kmail2 6.3.3 (24.12.3)

Operating System: Fedora Linux 42
KDE Plasma Version: 6.3.4
KDE Frameworks Version: 6.13.0
Qt Version: 6.8.2
Kernel Version: 6.14.2-300.fc42.x86_64 (64-bit)
Graphics Platform: Wayland
Processors: 8 × Intel® Core™ i5-1035G1 CPU @ 1.00GHz
Memory: 15.2 GiB of RAM
Graphics Processor: Intel® UHD Graphics

ADDITIONAL INFORMATION
This started happening about 3/4 months ago, can't remember the exact kmail version at the time.
I have 5 email accounts configured the same way, 3 on a dovecot server and the other 2 on a courier server.
The problem is random: one day everything's fine, the next day 2 random accounts redonwlonad emails, the next day another account (and only that one) shows the same behaviour.
Sometimes it downloads a few emails, other times more than a hundred.

In the past I tried configuring one account via IMAP but it didn't even work, the most success I had was that I could see emails in subfolders but not the inbox, so cahging to IMAP is not a solution for me.