I was going to self host my email server, but somehow my email provider (Migadu) is cheaper than a VPS ($19 USD per year) and offers custom domains, catch-all, and unlimited addresses.
Do not set the heap size to more than 8GiB, even if using heavy modpacks. Anything above 8GiB actually makes the game run worse, unless you have tons of players, because of GC lag.
Go to https://minecraft.wiki/w/Tutorial:Setting_up_a_Java_Edition_... for how to create a vanilla server for Minecraft Java edition (which is the best version, but is only on Windows and MacOS and Linux, unlike the significantly inferrior bedrock edition, which is way buggier but is avalible elsewhere).
I couldn't read this article because Science.org left Bot Fight Mode or Super Bot Fight Mode enabled in their Cloudflare settings, causing me to be blocked by a “security verification”. If you use Cloudflare, disable bot stop modes by going to dash.cloudflare.com and selecting your domain and then clicking on “Security” and then clicking on “Settings” and then using the buttons to disable Bot Fight Mode or Super Bot Fight Mode.