Forum Moderators: phranque
I researched it some and it sounds great. I turned it on and the spam went from several hundred a day to 5 or so.
I only have one big concern. What is the chance a users (legitimate) e-mail will be sent back and their agent/server not send it again?
As much as I want to get rid of spam, it's not worth loosing customer e-mails over.
It is a good assumption that legitimate mail will always be retried at least 3 times, and probably for at least 3 days. But it's a bad assumption that retries will be sent from the same IP address.
This is noted in the spec:
Another issue occurs when a large organization uses a pool of outbound mail servers for sending email to a system using Greylisting. If the pool is configured so that the same mailserver (with the same IP) will always retry deliveries for a particular mail, there is no issue. ...
When you think of the amount of mail AOL, Hotmail, etc. must send in an hour it would be a necessity to use multiple servers. Also, those are the same domains that many customers use.
