http://w25rxxn62dgix7qdbw4ot37m2y4ty7kxfrinspw4ce7jzse7pb6rhaqd.onion
To increase your privacy, we do not relate account data in any way, meaning inter-account communication isn't technically possible. If having a dedicated message history is important, one solution could be for both parties to create Hush Line accounts that will only be used for that conversation.