[exim] mbox creation

Dear user,
As per the email talk this morning, as you dont currently
have an mbox file, I'm going to create an empty one for you
tonight (probably around 11pm).

If your mailer is currently configured to use IMAP, then
it will automatically begin to use the mbox next time
your INBOX is opened.

If it's currently configured to use POP, then the mbox
wont be used until you switch to IMAP.

Users of 'direct' mailers can ignore this msg for now.

Terry.