I've been thinking about a challenge-response email
authentication scheme for quite a while. [IUnknown.com:
John Lam's Weblog on Software Development]
I’m
running Matador
from MailFrontier for about a month
now and I’m happy with the results. This product uses challenge-response technique
to handle border-line spam by sending a picture of three cats and asking the
respondent to count them and reply with an answer. I’ve noticed that only
a small fraction (1%) of the spam is interpreted as border-line and causes
Matador to send out the challenge. After a rocky start (crash on startup on
W2K) I’ve installed it on XP. It integrates nicely with Outlook and works
really well for me. I’ve got 2-4 false negatives (spam in my inbox) per
week.
I recommend
it for anyone running Windows XP and Office XP. They offer a free trial.
