fosstodon.org is one of the many independent Mastodon servers you can use to participate in the fediverse.
Fosstodon is an invite only Mastodon instance that is open to those who are interested in technology; particularly free & open source software.
If you wish to join, contact us for an invite.
@hebster Good question! I don't have a great way of knowing for sure since an encrypted email using that form looks the same as a standard one. Though honestly I only get a small handful of encrypted emails every year.