Logged In: YES 
user_id=469548

mailgw now accepts registration confirmation mail that
contains the following in the subject line:
-- key <32-char otk, such as Aj4euk4LZSAdwePohj90SME5SpopLETL>.

I suppose we should send another email after confirmation,
to confirm that the confirmation was successful.. :)

However, before I do this, I would like to extract all code
related to sending mail to a new module, mail.py. The code
is now spread over client.py and mailgw.py, and there's
quite a bit of duplication. Richard, are you okay with this?