Are you using the Import/Export Settings
buttons in the settings page?
If you can reproducibly crash an instance then you should definitely file this as an urgent security issue in the lemmy repo so it can be fixed: https://github.com/LemmyNet/lemmy/issues
(Federated) email didn’t survive. It got completely subsumed by the major providers who now have control over everything email related. It’s now impossible to run your own email server since none of the major providers will deliver your email without your mail server having first built a reputation.
The fediverse analogy would be if 99.9999% of users were on Threads and you couldn’t interact with any of those users from any of the small independent fediverse servers. Frankly, that’s exactly what it looks like is happening.