I just received an email with a challenge:

https://customercare.cloud9.net/mailchallenge.cgi?challenge-id=1a5c5c49cc768146756106f3573a36c3

Challenging would have been fair if I tried to send an email to the person
in question (whomever it might be). However, I answered a question at the
mailing list IBObjects@yahoogroups.com, a mailing list that has over 1500
subscribers. It would be ridiculous if every member posting to this list
had to answer a challenge for every member that used cloud9 (luckily, I
think it is just one person who recently subscribed). I don't know whether
it is you or your clients fault (I suspect the latter), but please take
appropriate action anyway (that action being either making sure that mails
to ibobjects@yahoogroups.com gets through, or telling us whom (email
address) makes the challenge so that we can ban him/her from our list.

Yours faithfully,
Svein Erling Tysvær