Luke S Crawford wrote:
considering just how many people use greylisting, this is likely a bad idea. Greylisting works by rejecting the first message from a new server with a 4xx (temporary) error code. If the server tries again immediately or never tries again, it's probably a spammer. If the server waits a reasonable period of time (say, 30 minutes) and then re-sends the mail, it's probably legit, and the greylist program puts that server on the whitelist so mail from that server goes through right away next time.
Many people set things up such that if you try again immediately, you get put on a blacklist, as you are probably a spammer.
I really don't understand why people just don't turn off their mailservers if they don't want mail from others.
Ralph