For those self-hosting a lemmy instance, what hardware are you using? I am currently using a small Hetzner VPS. It has 2 vCPU, 2GB RAM and 40GB SSD storage. My instance is currently just in testing with me as the only user, but I plan to use it for close friends or family that may want to try this out, but might not want to sign up for a different instance. My CPU and RAM usage is great so far. My only concern is how large the storage will balloon to over time. I’ve been up for ~20 hours and it’s grown to 1.5G total volume since.
I had this issue and the cause was the email server. If you’re using smtp you’ll have to make sure your vps opens port 25.
However you can also just register without an email and it should work