Hi Prabh, > Thanks for your advice, i actually know this. what would you say about > those who put there efforts to implement SPF. why they do it? *if* someone sets up SPF for their domain, SPF works. Among other things, it can greatly reduce the amount of backscatter you receive due to spammers using your address to send mail. So it's not futile at all, it's just not planned to be used the way you intend to do it. Which SPF implementation are you using? And on which CentOS release? Best regards, Peter.