From official forum: *Update*
There will be a known issue once the servers will be back up.
If you use the transfer money system by use of the mail system, you will receive an error message.
If you then try to use the ingame mailing system again, the message will reappear, blocking you until logging out from any further attempts.
This is known and will be fixed at a later date.
Players are to be adviced NOT to use the send money function at all until this has been fixed.