Date: Thu, 2 Jun 2005 07:52:19 -0400 From: Bart Silverstrim <bsilver@chrononomicon.com> To: "Chad Leigh -- Shire.Net LLC" <chad@shire.net> Cc: Jorn Argelo <jorn@wcborstel.nl>, FreeBSD Mailing List <freebsd-questions@freebsd.org> Subject: Re: postgrey question Message-ID: <c4c21b43f2389dad9ec03c5750af3189@chrononomicon.com> In-Reply-To: <6ADE561C-FF8C-42B8-ABD8-B06AB10DA78F@shire.net> References: <0a6397740f09ea4ac7cce0b1bead3bde@chrononomicon.com> <8B6C5637-F4B3-4635-94EA-F1B8EE9D8A2F@shire.net> <429E25BB.9080006@wcborstel.nl> <6ADE561C-FF8C-42B8-ABD8-B06AB10DA78F@shire.net>
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On Jun 1, 2005, at 5:25 PM, Chad Leigh -- Shire.Net LLC wrote: > > On Jun 1, 2005, at 3:16 PM, Jorn Argelo wrote: > >> Chad Leigh -- Shire.Net LLC wrote: >> >> >>> >>> On Jun 1, 2005, at 8:07 AM, Bart Silverstrim wrote: >>> >>> >>>> I've been looking into ways of improving our spam filtering. >>>> Currently I'm running postfix with amavisd-new (spamassassin and >>>> clamav), and saw an article on greylisting using postgrey. Turns >>>> out there's a port for it already in FreeBSD. >>>> >>> >>> >>> >>> I don't run postifx and the thing I am about to mention I have not >>> tried yet, but you may want to explore modifying your greylisting to >>> be based on spamassassin results. >>> >>> I use exim as the mta and there is a thing called sa-exim that lets >>> you run spamassassin at SMTP time so that you can reject mail if you >>> want before you actually are finished receiving it. The author of >>> sa- exim has modified it to do greylisting based on spamassassing >>> scores generated at smtp time, so that you only greylist mail that >>> is thought to be spam and do not inconvenience your regular users. >>> >>> Can you do spamassassin at smtp time with postfix? >>> >> >> >> That's far too complicated. Postgrey does an excellent job. > > Yes, normal greylisting works for some people, but in general, it is > not seconds, but minutes (I don't believe that your server tells it > how long to wait, but rather in general greylisting it returns a 4xx > temporary failure error and the sending mail server will automatically > retry within its own retry rules) and lots of people do not like to > have their good mail greylisted at all as it can delay good mail for > minutes or longer, so the one I described above is a modification on > greylisting that allows it to only greylist possible spam and not all > mail. If I understand the postgrey docs correctly, there is a mechanism where it'll automatically whitelist common IPs from which mail is accepted, so the greylisting is more of an adaptation period. But I could be mistaken and confusing it with another greylist system...
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