Be really careful when blocking servers (aka "domains") on Mastodon. If you block an entire server, this will also remove all your follows and followers on that server.
If you have accidentally blocked a server and you wish you hadn't blocked it, here's a guide for what to do next:
➡️ https://fedi.tips/help-ive-accidentally-blocked-a-server-on-mastodon-what-do-i-do-now
Obviously this isn't ideal, and it's better not to accidentally block a server, but hopefully this provides some kind of way back if the worst happens.