This idea is thanks to a friend that always rebuilds his server rather than update it from build to build. The idea is that if I'm in their contact list they can send a message to me since they know my UID and that I will connect to that server. The thought is that he would send me a token, or tokens, to get my permissions back in case I reconnect while he is not online.

Basic idea is that if the UID of the client is not found in the clients table prompt the user that the "User is not found in {server name}'s database" and ask if they are sure they want to send via this server any way instead of the current error message. If they select Yes add the UID to the clients table with unknown nick (maybe use nick from contacts list if possible), get the clid and insert the message to the messages table.