Our Mailman 3 installation on a Debian Trixie virtual machine is crashing at random intervals. The stack currently runs Mailman3 alongside Python 3.13, protected by iptables and fail2ban. I need someone who truly knows Debian internals, Mailman3 architecture and Python debugging to locate the root cause, restore stability and lock the box down against known (and unknown) Mailman-related exploits. You will have full SSH access so you can: • comb through systemd, Mailman, Postfix and kernel logs to pinpoint the fault; • verify every package dependency and rebuild/re-install anything corrupted; • harden iptables, confirm fail2ban jails are effective and patch any CVEs that apply to Mailman3 or its Python environment; • produce a concise report that explains the failure, documents each remediation step and lists any further actions I should schedule. Acceptance criteria 1. Mailman3, web UI and mail delivery run for 72 h without a crash. 2. The written report is delivered in Markdown or PDF and is clear enough for another admin to replicate your work. If you’re comfortable working directly on a production VM and can wrap this up quickly, let’s talk so I can hand over access details.