This is a confusing topic that should be viewed from the perspective of the Skiff suite and not just Skiff Mail. As it was explained to us by Skiff Support, Skiff has decentralized identity, key ownership, and storage. When you log into another email service, you do so with an identity that belongs to that service. For example, when you log into Gmail, you use a Gmail address, which of course belongs to Google. You can log into Skiff with a Skiff address, but you can also log in using a Web3 address like a MetaMask wallet or an ENS name. These identities do not belong to Skiff. Skiff uses public key encryption to protect your data. Those keys belong to you, not to Skiff. Finally, while your data is normally stored on Skiff's servers, you can elect to store your data using the Interplanetary File System (IPFS). IPFS is a storage system that distributes your encrypted data across the internet in a decentralized fashion. One of the goals of the Skiff team is to eventually offer a version of Skiff that can function using IPFS completely independent of Skiff's own servers.