You may be confusing Mastodon/ActivityPub for an earlier predecessor such as OStatus. Mastodon DMs aren't visible in any feeds but those of the the persons @ m

You may be confusing Mastodon/ActivityPub for an earlier predecessor such as OStatus. Mastodon DMs aren't visible in any feeds but those of the the persons @ mentioned. It is sent straight to their personal "inbox". The Mastodon clients often interleave that in that user's "Home" timeline, but they are the only person that sees that and it comes from a different "inbox feed" than normal public post "pulls". There's a bunch of recent drama about "instance admins can see DMs" because they are stored in plaintext in the database, but there is absolutely no admin tool to read those in normal casese and any admins reading DMs are doing so directly out of the instance database (and no different from Twitter contractors who have access to Twitter's DBs and thus Twitter DMs). (The one tool that will push a DM to an instance admin's direct in-app visibility is the spam/harassment reporting tool, when a user has requested their admin take a look at something.) The other recent DM drama on Mastodon is that most clients including all the official ones and the Mastodon web client itself intentionally confuse DM recipients and @-mentions to simplify the UI. Which also means that you can't "blindly" @-mention a third party in a DM without (often accidentally) sending the DM to their inbox. "Followers Only" posts are similar technically: they get posted directly to followers' "inboxes" and do not show up on any public feeds. Again, most clients "merge the streams" on the "Home" timeline and make it appear like a single source timeline, because most of the time that is a better/more preferred user experience. but there's still a technical difference in ActivityPub between toots your instance has pulled from a public feed and toots your account (actor, in ActivityPub parlance) has directly received in its inbox. ActivityPub covers both parts: RSS-like microblog syndication and Email-like inboxes/outboxes. (ETA: The easiest place to read up on it yourself is possibly the ActivityPub spec itself. It is dense, but well written and reasonably easy enough to follow. Darius Kazemi's notes on the ActivityPub spec may help depending on your familiarity with other W3C specs, including and such as JSON-LD.)