The system creates what is referred to as a triplet. Which is a hash value of the sending server, the mail from and the rcpt to.
This is put in memory and there is a time window in which the same triplet must come again to be passed on. Once a triplet makes it
through, then that triplet is remembered for some settable amount of time. See
http://www.greylisting.org for more information.
Most spam is not retried, some is retried once or twice real fast and then the
sending machine gives up.
This actually works pretty well.
Stuart D. Gathman wrote:
On Mon, 22 Aug 2005, Scott Kitterman wrote:
With some minor exceptions and some assembly required there is a Linux
equivalent of this.
When greylisting, how do you know when you are seeing the same message again?