[aclug-L] Re: Using RBL on Email server

[Steven Saner <ssaner@xxxxxxxxxxxxxxx>]

Dale W Hodge wrote:
> I know this is probably going to be a question that most of you can't 
> answer, but has anyone else on the list tried using RBL's on their mail 
> server?  If so, which have you liked and which do you not?
> 
> For those wondering what I'm asking about, I'm referring to using 
> Realtime Black Lists on my mail server to try and stem the tide of spam 
> email. The concept is to reject the message at the gateway by consulting 
> a list of known and/or potential spammer IP's rather than using 
> filtering software to try to deal with the messages after they've been 
> delivered. The problem as always is one of how much do you trust a list 
> to be accurate. Using a conservative list has helped some, but now 
> wondering which lists are more aggressive without being too aggressive.

As already mentioned, using an RBL to reject mail can be a little dangerous. 
Maybe not for a personal mail server, but for a corporate/ISP mail server you 
can start to reject too much legit mail.

Also already mentioned is greylisting. Greylisting is great. Very effective at 
stopping spam and stops very little legit mail because the sender side will 
resend the message again and it will get through. It's downside is that mail 
gets delayed, which can be a problem.

So here's the secret. Combine them. Greylist. But only greylist certain 
messages. Messages that are suspect, such as being on an RBL. You can use more 
agressive RBLs because the message will get through if it is legit. And most 
legit mail will not be delayed at all.

Steve

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Steven Saner <ssaner@xxxxxxxxxxxxxxx>

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