> Paul, I appreciate what you're saying above. But isn't it likely that if spammers > are going to the trouble to add SPF records that they're also going to the > trouble to retry after a tempfail, and thus defeat greylisting?
Yes, some are already doing this. However, I suspect that others are now smart enough to realise that anyone doing greylisting is probably also ahead of the game on content filtering, so retrying is a waste of time. Alternatively, they may be smart enough to realise that a "go away spammer" response from a system they do get through to is unlikely to change if they retry with a different address or similarly spammy content, so they may update their lists to provide a smaller address database which has a much higher confirmed delivery rate. Business advantage and all that... > The case that I was trying to check for was the case where the spammer > sends through a proxy or a zombie and otherwise impersonates > the sender. That's virtually impossible to check for, which leaves us with content checking. Paul. -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.1.371 / Virus Database: 267.14.16/225 - Release Date: 09/01/2006 _______________________________________________ NOTE: If there is a disclaimer or other legal boilerplate in the above message, it is NULL AND VOID. You may ignore it. Visit http://www.mimedefang.org and http://www.roaringpenguin.com MIMEDefang mailing list [email protected] http://lists.roaringpenguin.com/mailman/listinfo/mimedefang
