If any Mastodon admins are dealing with spam account sign-ups, it's worth noting that these accounts seem to universally use disposable email providers and burner email address. There's a GitHub repo that tracks these providers. All moderation inquiries are sent to a user's email on Mastodon, so there's no legitimate reason any Mastodon user should be using a disposable email address. As such, there's a git repository that tracks these disposable email providers. There are also bash scripts that will import the repository into tootctl for you.
The disposable email git repo can be found here:
And the bash scripts can be found here:
Simply clone the repo and copy the bash script onto your server, then edit the script to point at your Mastodon installation and the directory you cloned the repository to, and it should handle the rest.
Side note: I checked our logs and we had a huge spike in attempted sign-ups from a bunch of different disposable email addresses this week, so I can confirm that blocking them definitely works. :blobyeengrin: