If the sender is a legitimate server they will follow RFC guidelines and within a few minutes they will try to send mail which will be delivered. All the tools you probably get to know will do the job when used together: some well designed Gmail filters wont hurt and turning on smart tags will also work wonders. After leaving habeas Anne was founded and joined ISIPP creating a neutral place where e-mail recipients and email senders can come together to manage Internet public policy and email delivery issues when I get something I really dont want or from a Persistent spammer I met them back with canned responses and then create a filter so that all the emails I get from that address also get the same canned responses. Our database analyzes this data in real time and will block IP addresses that have sent large amounts of junk mail to several places around the world in the spam of the preceding minutes.If the sender is a legitimate server they will be following the RFC guidelines and within a few minutes they will retry sending the email which will be then delivered.All of the tools youre likely familiar with will do the job when used together: Some well designed Gmail filters wont hurt and turning on smart labels will also work wonders.After leaving Habeas Anne founded and joined ISIPP creating a neutral place where email receivers and email senders could come together to deal with Internet public policy and email delivery issues.When I get something I really dont want or from a persistent spammer I hit them back with the canned response then create a filter so any email I get from that address also gets the same canned response.Our database analyzes this data in realtime and will block IPs that have sent excessive amounts of spam to multiple locations in the world in the spam of the previous few minutes.