Codger wrote: > Regardless of challenge-response or > greylisting, [...], the idea is the same...
No, those ideas are very different, both in practice, philosophy and results. One of them is intended as a verification of the sender, the other is intended to differentiate between connections from real queuing mailers and spambots/viruses. > My idea was to remove > the time delay and in the course of normal email communications > between known and accepted contacts, This is of course allways a nice thing to do. I don't see how your method would change the delay at all though. It still requires the mail to be analyzed by SpamAssassin and it has absolutely no impact on a greylist or challenge-response system. Here are a copuple of things we do, that does have impact on the delay: * For every mail sent *out* from our gateway SMTP sender, message-ID, From, Reply-To and Subject is saved in a database. * Incoming mail that seems to be a reply to outgoing mail bypasses out selective greylist. * We use a SpamAssassin plugin to give negative scores to mail that looks like replies to outgoing mail. * We also saves info on incoming mail that is verified by SPF, DKIM or DomainKeys. If there is a certain number of hams and no spams from a verified address, mail from that addresses can bypass both the greylist and SpamAssassin. * The greylist has some more checks to decide wether a mail should bypass it or not. Things similar to what the Botnet plugin checks for example. > I realize also that signatures can be excluded in responses, but they > don't have to be included in every response for the method to be > effective. I check the References and In-Reply-To on incoming mail against our database of outgoing mail. Those are pretty reliable signs that a mail is a reply. Of course, some pieces of software fails to insert those headers, so I also check the SMTP sender and recipient and the subject against the database. In the SA plugin I have three different eval tests so that I can give different scores depending on how likely it is that an incoming mail is a reply to an outgoing. This doesn't require anything at all from the user. Regards /Jonas -- Jonas Eckerman, FSDB & Fruktträdet http://whatever.frukt.org/ http://www.fsdb.org/ http://www.frukt.org/
