it's an anti-spam thing. basically, when it sees mail from a new sender or recipient or from a new place come in, it says "go away. i don't want to talk to you yet". and spam goes away and doesn't try again. whereas real mail tries again (as it should)
so in exchange for a couple of minutes' delay on legitimate mail from a new sender/source, it avoids thousands of spam messages per day without even having to process them on the machine.
Wow! I wonder if my IT person has ever heard of this. We've got some kind of thing that sends me an email about questionable emails that it's blocked, but some still get through.
I'm totally astonished that greylisting is still an effective first-line spam defense. I was sure that i would have already given up on it years ago. But the logs dont lie; it still manages to block over 95% of the incoming flood on my servers, so i continue to use it...
It makes sense - in order to deal with greylisting, spammers need to do twice as much work or more, which slows them down, and their game is all about number of messages sent per second. They rarely, rarely retry.
If they start trying a second time regularly, I'll just up the number of retries required. Short of requiring a sending mail server to perform some processing on my behalf, I can't think of a more effective spam deterrent than greylisting.
I've been running a greylisting agent on my Exchange server for a while now, and it cut down my spam by a factor of ten or so.
Occasionally, however, I run into some busted-ass mail server that doesn't retry properly, and then I get bounces. One of those busted-ass mail servers is the one that my in-laws use. Sigh.
Finally got it stable under Mac OSX 10.5. Very impressive, this plus the RBLs seems to get the spam. Which is good, I was averaging 50-100 a day even after the RBLs (T=bird would get those but the Ipod would be clogged with junk)
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timeasmymeasure
no subject
Date: 2009-05-07 03:36 pm (UTC)no subject
Date: 2009-05-07 03:52 pm (UTC)no subject
Date: 2009-05-07 04:13 pm (UTC)But if you're happy, I'm happy!!
no subject
Date: 2009-05-07 04:22 pm (UTC)so in exchange for a couple of minutes' delay on legitimate mail from a new sender/source, it avoids thousands of spam messages per day without even having to process them on the machine.
no subject
Date: 2009-05-08 01:54 pm (UTC)Like, probably 20 a day. Ugh.
*makes a note to check with her*
:D
no subject
Date: 2009-05-07 04:47 pm (UTC)no subject
Date: 2009-05-07 05:11 pm (UTC)If they start trying a second time regularly, I'll just up the number of retries required. Short of requiring a sending mail server to perform some processing on my behalf, I can't think of a more effective spam deterrent than greylisting.
no subject
Date: 2009-05-07 05:11 pm (UTC)Occasionally, however, I run into some busted-ass mail server that doesn't retry properly, and then I get bounces. One of those busted-ass mail servers is the one that my in-laws use. Sigh.
no subject
Date: 2009-05-07 07:52 pm (UTC)You go grrl! Smack those naughty emails!
no subject
Date: 2009-05-07 07:55 pm (UTC)RAAR! IN YOUR FACE, SPAMMERS.
no subject
Date: 2009-05-07 08:40 pm (UTC)no subject
Date: 2009-05-10 05:25 am (UTC)CZ