Mastodon's Federation Problem: Why Newsletters Break Across Instances

Mastodon's move into newsletters runs into a hard technical wall: federated delivery across hundreds of instances lacks the architectural simplicity of centralized platforms. Subscribing to a creator on one server while followers span many others requires solving bounce handling, unsubscribe propagation, and CAN-SPAM compliance through ActivityPub—a spec built for public posts, not guaranteed long-form delivery. Ghost has already shipped this; Mastodon's execution discipline will determine whether federation can bear the load.