Wouldn't a even simpler solution be to define a high MX record to a dummy address that would never answer. The spammers were going to retry, they would anyway and a real server would retry for sure.
- Re: Backup MX server Adam
- Re: Backup MX server David Terrell
- Re: Backup MX server Constantine A. Murenin
- Re: Backup MX server Randal L. Schwartz
- Re: Backup MX server Peter Fraser
- Re: Backup MX server Randal L. Schwartz
- Re: Backup MX server Rod.. Whitworth
- Re: Backup MX server Lars Hansson