I can't help with anything to do with the floods, but on personal messages, you need to make a few normal posts before they're unlocked for you. At the time of writing this Leah, as a new member, has only made one, which probably explains the 'mailbox full' message.
The solution to this is either to continue to discuss on the public forum, or for Leah to make a few more posts in order to unlock them. Short posts in this thread, such as "Thanks" or "I'll get back to you on this", should be enough (as I understand it).