migrate eugeni to the gnt-fsn cluster
This is a big decision, but we might want to consider migrating eugeni out of kvm4 in the short term.
This server is highly critical: it handles incoming mail and mailing lists, and any downtime on that server is felt quickly by everyone in the Tor project.
Even though the gnt-fsn server is over-provisionned, it is technically more reliable than a single machine like kvm4 because it has redundant nodes. We might be able to afford the extra space to host eugeni right now.
The risk, of course, is that eugeni is an old server that is very important infrastructure. Migrating it might be tricky. For example its IP address might be hardcoded in a bunch of places, and moving it to the gnt-fsn will mean changing that IP address.
Such an IP change might also affect its reputation with other mail servers, making mail delivery even harder than it already is.
But we have to cross that bridge anyways with the new SMTP delivery service in #30608 (moved).