Just logged on and looked at my Inbox, and Sent box, in which there were a whole bunch of messages, a good number of which I'd saved.
I browsed around the site, including chatroom, and went to reply to a message I'd recently received and every, and I mean every, of my e-mails had gone from the Inbox and Sent folder. Not even ones sent/received inside the last 30 days were there!
WTF happened as it certainly wasn't anything I did!!