They add: > Additionally, blocking a user who has access to a profile key will trigger a profile key rotation. People who don't know you can't use the new sen

They add: > Additionally, blocking a user who has access to a profile key will trigger a profile key rotation. People who don't know you can't use the new sender privacy beta feature, but if you are willing to risk spam then you can allow everyone to use it: > users who want to live on the edge can enable an optional setting that allows them to receive incoming “sealed sender” messages from non-contacts and people with whom they haven’t shared their profile or delivery token. This comes at the increased risk of abuse, but allows for every incoming message to be sent with “sealed sender,” without requiring any normal message traffic to first discover a profile key.