Hi All
We've recently implemented Greylisting on our border mail servers.
This asks sending mail servers to wait and try again in a few minutes. Spam engines hate that and give up, moving onto their next target.
The upside is that fewer than 30% of attempted spam deliveries persist. The downside is that legitimate mail is inconvenienced for a short while.
We whitelist persistent delivery servers whose content is then passed to the spam filtering servers so that regular deliveries then bypass the initial Greylisting hurdles.
The SMTP RFCs dictate that a sending server should not wait less than 5 minutes and no more than 2 hours to re-try. So, before they join the running Whitelist a sending server might exhibit a little delay in delivering.
We've been monitoring them very closely since then went into service and we're very pleased with their performance.
regards
Simon
Discussion of this announcement should be made in this (http://www.idnetters.co.uk/forums/index.php?topic=4621.msg76292#msg76292) thread.
Thanks.