> > If they are online then I do forward callouts to see if the recipient > is valid and based on that I would return a 550 at connect time > indicating an invalid account.
And return a 450 if the callout connection times-out , I guess ? On the primary MX too this may be already being done, Will that double callout make the delay too long The major problem , in such an architecture is the reporting. Customers may get a little fussy when they dont see one particular mail and may ask for reports By my experience I see that more work is done on reports than on antispam in any solution. Do you plan to pass on reports too from your free MX, BTW Marc, Do you think this is all really worth it ? See your spamgraphs, At least for me spams have been going down since the beginning of the year. Even before McColo :-) . I am assuming as ISP's around the world get stricter with their clients spams will still reduce further. All the pill spamming you see may be a thing of the past. Just like today we dont see any of the stock spams as before ( I dont know why though ? ) Antispam will be a low end commodity service like antivirus is today Thanks Ram PS: If you want to increase your business , diversify or get another real job
