Scam-grey 1.5

Scam-grey is a milter which filters mail originating from MS Windows hosts. Scam-grey filter provides you the ability to mitigate the flow of unwanted email from such hosts using grey listing.

How it works:
On the first delivery attempt from a Windows host, Scam-grey generates a temporary error message. Subsequent delivery attempts made after the delay period will be allowed through. Unlike standard mail servers, virus, trojan infected hosts and zombies are not designed to retry the delivery after a temporary failure.

Scam-grey pairs

the helo string
the IP address of the sending server (host)
as a record and returns a temporary failure (SMTP code 450 extended code 4.7.1) if the host is greylisted.

The record is expired if there is no connection for the matching record within the next 24 hours. Click here to see a sample of mail servers which are currently greylisted