No its not visible to the receiver after syncing with server.
Thanks, good to know, what if a conversation has been started, and the message has been answered by the receiver, what happens to these messages?
Not sure what do you asking, please try to test it yourself and see how it works in your case.
Is it not possible for administrator to bulk delete messages, they are filling the database, especially if there are image attached?
It would be nice with an auto delete messages function eg. after a month or a year?
Not yet, that will be developed abit later.