. on Nostr: what is email for?

{ "id": "51e63307eb7a8b4aca2c5d22c06e5183349db18c5890f11ba2e96a3a117c9e6a", "pubkey": "edb470271297ac5a61f277f3cd14de54c67eb5ccd20ef0d9df29be18685bb004", "created_at": 1726605957, "kind": 1, "tags": [ [ "e", "1f2b76960024f5b99353eabdab9888d00151b774fabb4eed428116bd0b49af99", "", "root" ], [ "p", "460c25e682fda7832b52d1f22d3d22b3176d972f60dcdc3212ed8c92ef85065c" ] ], "content": "what is email for?", "sig": "40b291697df8abd03fa87aae11f261cb7d31de577669a2d1d0db1156d684ade7162b132d7c16ea377e9d1d69d4233fdde9513178b8ab77a620e28a5fff8db5ff" }