[webmin-l] I have found out the reason why Postfix keeps getting killed by OOM Killer

[Turritopsis D. T. En M. <teo...@pr...>]

Subject: I have found out the reason why Postfix keeps getting killed by OOM Killer

Good day from Singapore,

On 1st March 2025 Saturday, my Postfix service stopped responding. When I executed the "systemctl status postfix" LINUX command, it shows that postfix was killed by the OOM Killer.

To solve the problem, I tried restarting the postfix service but it did not solve the problem.

Then I tried rebooting my Virtual Private Server (VPS) in Germany but it did not solve the problem.

As a last resort, I tried uninstalling and reinstalling postfix but it did not solve the problem as well.

My postfix service was consuming 6.2 GB of RAM before it got killed by the OOM Killer. The total amount of physical memory (RAM) my VPS has is only 8 GB. No wonder my postfix service keeps getting killed by the OOM Killer. Is this a Denial of Service (DOS) attack?

This morning, on 2nd March 2025 Sunday, I suddenly had an idea. I started checking the Mail Queue. There were 115 messages stuck in the Mail Queue! After some deliberation, I decided to clear the mail queue.

After clearing the mail queue, my postfix service resumed normal service and no longer gets killed by the OOM Killer. Clearing the mail queue actually solved the problem!

But until now I still have no idea why 115 messages stuck in the mail queue will cause postfix to consume ENORMOUS amounts of RAM and cause it to get killed by the OOM Killer. OOM = Out of Memory.

Could somebody explain why? Do you think my Virtualmin VPS server has been compromised by Advanced Persistent Threat (APT) hackers?

I am looking forward to your reply. The last time my postfix service stopped working due to a similar OOM condition was on 11 Jan 2025 Saturday, as posted earlier.

Thank you.

Regards,

Mr. Turritopsis Dohrnii Teo En Ming
Targeted Individuals in Singapore
GIMP = Government-Induced Medical Problems
2nd March 2025 Sunday