Hello, The way I understand "greylisting" it will have to be implemented at the MTA level, so I am not sure it could be implemented in spamassassin. Nonetheless, for all the initial negative reaction in this forum, "greylisting" is a fantastic new proposal which will be implemented at many sites. Attached is an email that was recently sent to admins on our campus requesting discussion on the matter. I attach it here since it is very informative on the subject.
Sincerely,
- Henrik
And, from your attached message:
The main tenet of the proposal is to move the burden and expense of the queuing to the sending system temporarily to make sure they are a real mail system, after which everything happens as it does now.
[As you read this, note that local-hosts will be pre-white-listed for no delays ever.]
The way the remote site is forced to queue the message temporarily is that when a new message gets offered from a remote host out host uses a database to note the sending IP, and the sending and recipient e-mail addresses. Our side answers the attempt to send with a 400-level "TMPFAIL" answer that says "I should be able to accept this message; but, I can't do it right now, please try again later" as defined in the SMTP protocol. The remote site will queue it and try to re-send again later. At least an hour later (by default), when the same host using the same e-mail addresses tries to resend the message, the message will be accepted just like happens currently and that triplet of information is marked in the database so that future e-mail will pass through with no delay.
So, you are lying to the sending MTA. The message "temp fail" is false. There is no temporary failure. You are rejecting on arbitrary rules. My, my. What is the internet coming to? Since the spammers are lying, we will lie to every mail server that attempts to contact us. Then, we will arbitrarily change our mind for one particular from/to pair. When you connect again, I will lie and "temp fail" your message for this different from/to pair.
Does anyone see the flaw in this logic? You are creating arbitrary rules at the MTA level and (by design) increasing the burden, workload, and costs to innocent mail servers. BY DESIGN!
If this is how desperate you've become, I'm sorry for you. You are going to penalize every sending MTA in the world because you can't find a better method _right_now_.
Lack of a better solution should NOT justify implementation of a pseudo-solution.
If more admins start to adopt the "grey"listing technique, we will be faced with spammers who send their messages twice or thrice. This means that non-"grey" locations (like mine) will be inundated with double or triple the amount of spam to filter.
THANKS! Just what I need. A university who doubles the workload of my sending MTA, and who convinces spammers to increase the level of spamming.
Also, seeing as this is designed as an MTA-level SMTP reject/accept mechanism, it is in no way related to SpamAssassin.
I hope that somebody will actually plot the logic, instead of Bob's attitude of insulting me because I don't agree with him. If you did an RFC, believe me, you will get many more comments attacking the logic.
Sincerely, - Alan Leghart
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