| One possibility is to list your primary again as the tertiary, possibly | under a different name and/or IP address. Spammers that deliver in reverse | MX order will still end up trying to deliver to your primary first.
I tried this and it resulted in mail loops when one of the servers was down. I like the suggestion below better. QQQQ | You could also list a bogus server in IP "dark space" (ie. an address known | to have no listening server) so that the spammer must first check the empty | address first. Even better is when there's a host there that drops packets | (no TCP reset or ICMP port unreachable reply) to port 25, so that the | spammer must time out the TCP connection attempt. | |
