About a couple of months ago I wrote a note to this list describing our experiences with grey listing. I'll briefly summarise it again. We did not start with a white list instead we selected those addresses that we would grey list. Postfix allows series of rules: 1/ if no reverse dns then greylist 2/ if reverse dns matches a large Regular expression designed to catch most dynamic, broadband etc. then greylist 3/ pass for normal handling This worked very well for us cutting the amount of spam we accepted to well under half. But remember that grey listing is merely a stop gap measure as soon as spammers think that greylising is really hurting them they will rework their spam engines to handle retries -- it won't be that difficult, particularly since they don't have to queue whole messages, just a message id and 'sender' and recipient. Russell.