Craig Whitmore wrote:

If anyone else has tried greylisting before , or has any comments on it, let me know.

There are basically too many broken "legitimate" sending SMTP servers i.e. won't retry for 4hrs+ etc. This will cause you major issues with regards to "but I sent your boss an email hours ago" and so on. Depends on what environment your recieving mail for etc. Cheers, James. p.s. this list not setting the reply-to feild is really annoying.

On Tue, 14 Feb 2006, Craig Whitmore wrote:

If anyone else has tried greylisting before , or has any comments on it, let me know.

Personally I find greylisting a pain. I am subscribed to a couple of lists that use it and it's annoying when my reply to the list takes half an hour to get through instead on 2 minutes. One important thing to watch for is that for larger sites the server that first tries to send your email might not be the one that tries to resend it later. Greylisting sites will thus block the email for a while until the sending site gets lucky and uses the same machine twice in a row. Generating random error messages to sending sites is just asking for trouble IMHO. You really can't determine exactly they will act and how long they will take to retry to send the message. Any delay is 100% your fault although most people using greylisting seem keen to push the blame to the sending site. It's the equivalent of ignoring someone when they first email/call you and saying "If it's important they'll ring back" . Not very polite and possibly not providing the best service to customers. -- Simon J. Lyall | Very Busy | Web: http://www.darkmere.gen.nz/ "To stay awake all night adds a day to your life" - Stilgar | eMT.

On Tue, Feb 14, 2006 at 01:10:29PM +1300, Craig Whitmore said:

I have been playing around with greylisting recently on a couple of test domains and it works pretty well (reduces the number of spam coming from malwared machines who don't retry sending their spam by over 90% before any spam checkers get to it), but I've noticed a number of real mail NZ servers not knowing what a 451 SMTP message is, and they treat it like a fail and they don't send the message again. (Yes I know I can whitelist good known NZ SMTP Serversto not Greylist from them)

If anyone else has tried greylisting before , or has any comments on it, let me know.

We've been using greylisting here for the last six months, and it's made a huge difference to the amount of noise that the downstream spam filters have to deal with. I've had to whitelist one external mail server, and a couple of internal ones, but all in all, I'm well pleased with the results. It's particularly useful to have running over mailman owner addresses to reduce the crap that arrives there. I would set your timeout to be really low - 15 seconds would be as effective as 30 minutes, as far as I can see. Cheers Si