This helps servers hosting many actors, and it helps us when delivering to lots of people on the same server; we only need to make 1 request per server.

This gets us a bit closer to seeing Mastodon's non-standard Mention activities.

I made a bit of an announcement to fediverse@lemmy.world: https://old.lemmy.world/post/12791602 Replies were delivered ok to my ActivityPub inbox and my mail inbox. And I replied to those from my email client, too!