I am applying greylisting and it really has some effects on the amount
of spam coming in.
I am running postfix with postgrey, and postgrey only has data available
from the envelope, such that Message_Id: information is not available. I
notice that in Freebsd greylisting is done using message-id:
I see the follwing scenaro for me: a zombie machine sends out spam for
me, and I greylist it and the zombie does not resend the message to me.
The the same zombie sends me another spam mail, and then this is
recognized by postgrey as the first message being resent, as it does not
know better. I have a feeling that this is going on in some amount of
cases, but I cannot investigate it as postgrey does not have access to
the info I would like to log.
So I ask you: would greylisting based on some unique id like Message-id:
lead to a better result?
And would there be problems issuing an error code like "file system full"
at the time of the "QUIT" command? I have heard that some genuine
MTAs would have problems with recovering from such a message at that
time. Which MTAs would that be?