To check if a server is part of the fediverse, fedifinder asks the server for the nodeinfo file (eg. https://mastodon.social/.well-known/nodeinfo). If a server doesn't respond to such a request, it's likely that it's not part of the fediverse. But it could also mean that it's currently down. Most of them are probably mail addresses. None of them are included in the export. Please follow them manually.
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